View source for Loops/Increment loop index within loop body

{{task|iterations}}
[[Category:Simple]]

Sometimes, one may need &nbsp; (or want) &nbsp; a loop which
its &nbsp; ''iterator'' &nbsp; (the index
variable) &nbsp; is modified within the 
<br>loop body &nbsp; '' in addition to the normal incrementation by the &nbsp; ('''do''') &nbsp; loop structure index''.


;Goal:
Demonstrate the best way to accomplish this.


<!-- ··· with a nod to Douglas Adams  (42 being the ultimate answer to THE question). !-->

;Task:
Write a loop which:
::* &nbsp; starts the index (variable) at &nbsp; '''42'''
::* &nbsp; (at iteration time) &nbsp; increments the index by unity
::* &nbsp; if the index is prime:
::::* &nbsp; displays the count of primes found (so far) and the prime &nbsp; (to the terminal)
::::* &nbsp; increments the index such that the new index is now the (old) index plus that prime
::* &nbsp; terminates the loop when &nbsp; '''42''' &nbsp; primes are shown


Extra credit: &nbsp; because of the primes get rather large, use commas
within the displayed primes to ease comprehension.


Show all output here.


;Note:
Not all programming languages allow the modification of a
loop's index. &nbsp; If that is the case, then use whatever method that
is appropriate or idiomatic for that language. &nbsp; Please add a note
if the loop's index isn't modifiable.


;Related tasks:
* &nbsp; [[Loop over multiple arrays simultaneously]]
* &nbsp; [[Loops/Break]]
* &nbsp; [[Loops/Continue]]
* &nbsp; [[Loops/Do-while]]
* &nbsp; [[Loops/Downward for]]
* &nbsp; [[Loops/For]]
* &nbsp; [[Loops/For with a specified step]]
* &nbsp; [[Loops/Foreach]]
* &nbsp; [[Loops/Infinite]]
* &nbsp; [[Loops/N plus one half]]
* &nbsp; [[Loops/Nested]]
* &nbsp; [[Loops/While]]
* &nbsp; [[Loops/with multiple ranges]]
* &nbsp; [[Loops/Wrong ranges]]
<br><br>

=={{header|11l}}==
{{trans|Python}}

<syntaxhighlight lang="11l">F is_prime(n)
   L(x) (2, 3)
      I n % x == 0
         R n == x
   Int64 d = 5
   L d * d <= n
      L(x) (2, 4)
         I n % d == 0
            R 0B
         d += x
   R 1B

Int64 i = 42
V n = 0
L n < 42
   I is_prime(i)
      n++
      print(‘n = #2 #16’.format(n, i))
      i += i - 1
   i++</syntaxhighlight>

{{out}}
<pre>
n =  1               43
n =  2               89
n =  3              179
n =  4              359
n =  5              719
n =  6             1439
n =  7             2879
n =  8             5779
n =  9            11579
n = 10            23159
...
n = 40   24876007075181
n = 41   49752014150467
n = 42   99504028301131
</pre>

=={{header|360 Assembly}}==
Assembler 360 provides 3 instructions to create loops: BCT, BXH and BXLE, the register which contains the loop index can be modified at any time. Nothing exceptional for an assembly, banning to modify the loop index begins with high level languages.<br>
This task is a good example of the use of ED instruction to format a number. 
For macro use (IF,DO,...), see [[360_Assembly_macros#360_Assembly_Structured_Macros|Structured Macros]].
<syntaxhighlight lang="360asm">*        Loops/Increment loop index within loop body - 16/07/2018
LOOPILWB PROLOG
         SR     R6,R6              i=0
         ZAP    N,=P'42'           n=42
       DO WHILE=(C,R6,LT,IMAX)     do while(i<imax)
         BAL    R14,ISPRIME          call isprime(n)
       IF C,R0,EQ,=F'1' THEN         if n is prime then
         LA     R6,1(R6)               i=i+1
         XDECO  R6,XDEC                edit i
         MVC    PG+2(2),XDEC+10        output i
         MVC    ZN,EM                  load edit mask
         ED     ZN,N                   edit n
         MVC    PG+7(L'ZN),ZN          output n
         XPRNT  PG,L'PG                print buffer
         ZAP    WP,N                   n
         AP     WP,N                   +n
         SP     WP,=P'1'               +1
         ZAP    N,WP                   n=n+n-1
       ENDIF    ,                    endif                  
         ZAP    WP,N                 n
         AP     WP,=P'1'             +1
         ZAP    N,WP                 n=n+1
       ENDDO    ,                  enddo
         EPILOG
ISPRIME  EQU    *                  isprime(n) -----------------------
         CP     N,=P'2'            if n=2
         BE     RETURN1            then return(1)
         CP     N,=P'3'            if n=3
         BE     RETURN1            then return(1)
         ZAP    WDP,N              n
         DP     WDP,=PL8'2'        /2
         CP     WDP+8(8),=P'0'     if mod(n,2)=0
         BE     RETURN0            then return(0)
         ZAP    WDP,N              n
         DP     WDP,=PL8'3'        /3
         CP     WDP+8(8),=P'0'     if mod(n,3)=0
         BE     RETURN0            then return(0)
         ZAP    J,=P'5'            j=5
LWHILE   ZAP    WP,J               j
         MP     WP,J               *j
         CP     WP,N               while(j*j<=n)
         BH     EWHILE             ~
         ZAP    WDP,N                n
         DP     WDP,J                /j
         CP     WDP+8(8),=P'0'       if mod(n,j)=0
         BE     RETURN0              then return(0)
         ZAP    WP,J                 j
         AP     WP,=P'2'             +2
         ZAP    WDP,N                n
         DP     WDP,WP               n/(j+2)
         CP     WDP+8(8),=P'0'       if mod(n,j+2)=0
         BE     RETURN0              then return(0)
         ZAP    WP,J                 j
         AP     WP,=P'6'             +6
         ZAP    J,WP                 j=j+6
         B      LWHILE             loopwhile
EWHILE   B      RETURN1            return(1)
RETURN0  LA     R0,0               rc=0
         B      RETURNX
RETURN1  LA     R0,1               rc=1
RETURNX  BR     R14                return to caller -----------------
IMAX     DC     F'42'              limit
EM       DC     XL20'402020206B2020206B2020206B2020206B202120'  mask
N        DS     PL8                n
J        DS     PL8                j
PG       DC     CL80'i=00 :  000,000,000,000,000'   buffer
XDEC     DS     CL12               temp for XDECO
WP       DS     PL8                temp for AP,SP,MP
WDP      DS     PL16               temp for DP
CW       DS     CL16               temp for UNPK
ZN       DS     CL20
         REGEQU
         END    LOOPILWB</syntaxhighlight>
{{out}}
<pre style="height:40ex">
i= 1 :                   43
i= 2 :                   89
i= 3 :                  179
i= 4 :                  359
i= 5 :                  719
i= 6 :                1,439
i= 7 :                2,879
i= 8 :                5,779
i= 9 :               11,579
i=10 :               23,159
i=11 :               46,327
i=12 :               92,657
i=13 :              185,323
i=14 :              370,661
i=15 :              741,337
i=16 :            1,482,707
i=17 :            2,965,421
i=18 :            5,930,887
i=19 :           11,861,791
i=20 :           23,723,597
i=21 :           47,447,201
i=22 :           94,894,427
i=23 :          189,788,857
i=24 :          379,577,741
i=25 :          759,155,483
i=26 :        1,518,310,967
i=27 :        3,036,621,941
i=28 :        6,073,243,889
i=29 :       12,146,487,779
i=30 :       24,292,975,649
i=31 :       48,585,951,311
i=32 :       97,171,902,629
i=33 :      194,343,805,267
i=34 :      388,687,610,539
i=35 :      777,375,221,081
i=36 :    1,554,750,442,183
i=37 :    3,109,500,884,389
i=38 :    6,219,001,768,781
i=39 :   12,438,003,537,571
i=40 :   24,876,007,075,181
i=41 :   49,752,014,150,467
i=42 :   99,504,028,301,131
</pre>
=={{header|AArch64 Assembly}}==
{{works with|as|Raspberry Pi 3B version Buster 64 bits}}
<syntaxhighlight lang="aarch64 assembly">
/* ARM assembly AARCH64 Raspberry PI 3B */
/*  program loopinc64.s   */
 
/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"

/*********************************/
/* Initialized data              */
/*********************************/
.data
szMessOverflow:     .asciz "Error: overflow !!!!"
sMessResult:        .asciz "Index  : @ Value  : @ \n"
szCarriageReturn:   .asciz "\n"
 
/*********************************/
/* UnInitialized data            */
/*********************************/
.bss
sZoneConv:                .skip 24
/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                             // entry of program 
    mov x20,0                     // counter
    mov x21,42                    // start index
1:                                // begin loop
    mov x0,x21
    bl isPrime                    // prime ?
    bcs 100f                      // error overflow ?
    cbnz x0,2f                    // is prime ?
    add x21,x21,1                 // no -> increment index
    b 1b                          // and loop
2:                                // display index and prime
    add x20,x20,1                 // increment counter
    mov x0,x20
    ldr x1,qAdrsZoneConv          // conversion index
    bl conversion10
    ldr x0,qAdrsMessResult
    ldr x1,qAdrsZoneConv 
    bl strInsertAtCharInc         // insert result at first @ character
    mov x10,x0
    mov x0,x21                    // conversion value
    ldr x1,qAdrsZoneConv 
    bl conversion10               // decimal conversion  ascii
    mov x0,x10
    ldr x1,qAdrsZoneConv
    bl strInsertAtCharInc         // insert result at second @ character
    bl affichageMess  
 
    add x21,x21,x21
    cmp x20,42                    // end ?
    blt 1b                        // no loop
 
100:                              // standard end of the program 
    mov x0,0                      // return code
    mov x8,EXIT                   // request to exit program
    svc 0                         // perform the system call
 
qAdrsZoneConv:            .quad sZoneConv
qAdrszCarriageReturn:     .quad szCarriageReturn
qAdrsMessResult:          .quad sMessResult
/***************************************************/
/*   Verification si un nombre est premier         */
/***************************************************/
/* x0 contient le nombre à verifier */
/* x0 retourne 1 si premier  0 sinon */
isPrime:
    stp x1,lr,[sp,-16]!        // save  registres
    stp x2,x3,[sp,-16]!        // save  registres
    mov x2,x0
    sub x1,x0,#1
    cmp x2,0
    beq 99f                    // retourne zéro
    cmp x2,2                   // pour 1 et 2 retourne 1
    ble 2f
    mov x0,#2
    bl moduloPuR64
    bcs 100f                   // erreur overflow
    cmp x0,#1
    bne 99f                    // Pas premier
    cmp x2,3
    beq 2f
    mov x0,#3
    bl moduloPuR64
    blt 100f                   // erreur overflow
    cmp x0,#1
    bne 99f

    cmp x2,5
    beq 2f
    mov x0,#5
    bl moduloPuR64
    bcs 100f                   // erreur overflow
    cmp x0,#1
    bne 99f                    // Pas premier

    cmp x2,7
    beq 2f
    mov x0,#7
    bl moduloPuR64
    bcs 100f                   // erreur overflow
    cmp x0,#1
    bne 99f                    // Pas premier

    cmp x2,11
    beq 2f
    mov x0,#11
    bl moduloPuR64
    bcs 100f                   // erreur overflow
    cmp x0,#1
    bne 99f                    // Pas premier

    cmp x2,13
    beq 2f
    mov x0,#13
    bl moduloPuR64
    bcs 100f                   // erreur overflow
    cmp x0,#1
    bne 99f                    // Pas premier
2:
    cmn x0,0                   // carry à zero pas d'erreur
    mov x0,1                   // premier
    b 100f
99:
    cmn x0,0                   // carry à zero pas d'erreur
    mov x0,#0                  // Pas premier
100:
    ldp x2,x3,[sp],16          // restaur des  2 registres
    ldp x1,lr,[sp],16          // restaur des  2 registres
    ret                        // retour adresse lr x30

/********************************************************/
/*   Calcul modulo de b puissance e modulo m  */
/*    Exemple 4 puissance 13 modulo 497 = 445         */
/********************************************************/
/* x0  nombre  */
/* x1 exposant */
/* x2 modulo   */
moduloPuR64:
    stp x1,lr,[sp,-16]!        // save  registres
    stp x3,x4,[sp,-16]!        // save  registres
    stp x5,x6,[sp,-16]!        // save  registres
    stp x7,x8,[sp,-16]!        // save  registres
    stp x9,x10,[sp,-16]!       // save  registres
    cbz x0,100f
    cbz x1,100f
    mov x8,x0
    mov x7,x1
    mov x6,1                   // resultat
    udiv x4,x8,x2
    msub x9,x4,x2,x8           // contient le reste
1:
    tst x7,1
    beq 2f
    mul x4,x9,x6
    umulh x5,x9,x6
    mov x6,x4
    mov x0,x6
    mov x1,x5
    bl divisionReg128U
    cbnz x1,99f                 // overflow
    mov x6,x3
2:
    mul x8,x9,x9
    umulh x5,x9,x9
    //cbnz x5,99f
    mov x0,x8
    mov x1,x5
    bl divisionReg128U
    cbnz x1,99f                 // overflow
    mov x9,x3
    lsr x7,x7,1
    cbnz x7,1b
    mov x0,x6                  // result
    cmn x0,0                   // carry à zero pas d'erreur
    b 100f
99:
    ldr x0,qAdrszMessOverflow
    bl   affichageMess
    cmp x0,0                   // carry à un car erreur
    mov x0,-1                  // code erreur

100:
    ldp x9,x10,[sp],16         // restaur des  2 registres
    ldp x7,x8,[sp],16          // restaur des  2 registres
    ldp x5,x6,[sp],16          // restaur des  2 registres
    ldp x3,x4,[sp],16          // restaur des  2 registres
    ldp x1,lr,[sp],16          // restaur des  2 registres
    ret                        // retour adresse lr x30
qAdrszMessOverflow:         .quad  szMessOverflow
/***************************************************/
/*   division d un nombre de 128 bits par un nombre de 64 bits */
/***************************************************/
/* x0 contient partie basse dividende */
/* x1 contient partie haute dividente */
/* x2 contient le diviseur */
/* x0 retourne partie basse quotient */
/* x1 retourne partie haute quotient */
/* x3 retourne le reste */
divisionReg128U:
    stp x6,lr,[sp,-16]!        // save  registres
    stp x4,x5,[sp,-16]!        // save  registres
    mov x5,#0                  // raz du reste R
    mov x3,#128                // compteur de boucle
    mov x4,#0                  // dernier bit
1:    
    lsl x5,x5,#1               // on decale le reste de 1
    tst x1,1<<63               // test du bit le plus à gauche
    lsl x1,x1,#1               // on decale la partie haute du quotient de 1
    beq 2f
    orr  x5,x5,#1              // et on le pousse dans le reste R
2:
    tst x0,1<<63
    lsl x0,x0,#1               // puis on decale la partie basse 
    beq 3f
    orr x1,x1,#1               // et on pousse le bit de gauche dans la partie haute
3:
    orr x0,x0,x4               // position du dernier bit du quotient
    mov x4,#0                  // raz du bit
    cmp x5,x2
    blt 4f
    sub x5,x5,x2                // on enleve le diviseur du reste
    mov x4,#1                   // dernier bit à 1
4:
                               // et boucle
    subs x3,x3,#1
    bgt 1b    
    lsl x1,x1,#1               // on decale le quotient de 1
    tst x0,1<<63
    lsl x0,x0,#1               // puis on decale la partie basse 
    beq 5f
    orr x1,x1,#1
5:
    orr x0,x0,x4                  // position du dernier bit du quotient
    mov x3,x5
100:
    ldp x4,x5,[sp],16          // restaur des  2 registres
    ldp x6,lr,[sp],16          // restaur des  2 registres
    ret                        // retour adresse lr x30
/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"
</syntaxhighlight>
{{Output}}
<pre>
Index  : 1 Value  : 43
Index  : 2 Value  : 89
Index  : 3 Value  : 179
Index  : 4 Value  : 359
Index  : 5 Value  : 719
Index  : 6 Value  : 1439
Index  : 7 Value  : 2879
Index  : 8 Value  : 5779
Index  : 9 Value  : 11579
Index  : 10 Value  : 23159
Index  : 11 Value  : 46327
Index  : 12 Value  : 92657
Index  : 13 Value  : 185323
Index  : 14 Value  : 370661
Index  : 15 Value  : 741337
Index  : 16 Value  : 1482707
Index  : 17 Value  : 2965421
Index  : 18 Value  : 5930887
Index  : 19 Value  : 11861791
Index  : 20 Value  : 23723597
Index  : 21 Value  : 47447201
Index  : 22 Value  : 94894427
Index  : 23 Value  : 189788857
Index  : 24 Value  : 379577741
Index  : 25 Value  : 759155483
Index  : 26 Value  : 1518310967
Index  : 27 Value  : 3036621941
Index  : 28 Value  : 6073243889
Index  : 29 Value  : 12146487779
Index  : 30 Value  : 24292975649
Index  : 31 Value  : 48585951311
Index  : 32 Value  : 97171902629
Index  : 33 Value  : 194343805267
Index  : 34 Value  : 388687610539
Index  : 35 Value  : 777375221081
Index  : 36 Value  : 1554750442183
Index  : 37 Value  : 3109500884389
Index  : 38 Value  : 6219001768781
Index  : 39 Value  : 12438003537571
Index  : 40 Value  : 24876007075181
Index  : 41 Value  : 49752014150467
Index  : 42 Value  : 99504028301131
</pre>

=={{header|Ada}}==
Ada does not allow the loop counter of a FOR loop to be modified in the loop. This example uses a simple Ada loop. The example also uses an Ada fixed decimal type to provide the comma insertion for the output.
<syntaxhighlight lang="ada">with Ada.Text_IO;         use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with Ada.Text_IO.Editing; use Ada.Text_IO.Editing;
with Ada.Numerics.Generic_Elementary_Functions;

procedure Main is
   type nums is delta 0.1 digits 15;
   format : String  := "zz_zzz_zzz_zzz_zzz_zz9.9";
   pic    : picture := To_Picture (format);
   package Nums_io is new Decimal_Output (Nums);
   use Nums_IO;
   type U_64 is mod 2**64;

   package mod_io is new Modular_IO (U_64);
   use mod_io;

   function Is_Prime (Num : U_64) return boolean is
      package Flt_Funcs is new Ada.Numerics.Generic_Elementary_Functions
        (Float);
      use Flt_Funcs;

      T     : U_64          := 2;
      Limit : constant U_64 := U_64 (Sqrt (Float (Num)));
   begin
      if Num = 2 then
         return True;
      end if;
      while T <= Limit loop
         if Num mod T = 0 then
            return False;
         end if;
         T := T + (if T > 2 then 2 else 1);
      end loop;
      return True;
   end Is_Prime;
   Prime_Count : natural := 0;
   Prime_Test  : U_64    := 42;
begin
   loop
      if Is_Prime (Prime_Test) then
         Prime_Count := Prime_Count + 1;
         Put ("n =");
         Put (Item => Prime_Count, Width => 3);
         Put (Item => Nums (Prime_Test), Pic => pic);
         New_Line;
         Prime_Test := (Prime_Test * 2) - 1;
      end if;
      Prime_Test := Prime_Test + 1;
      exit when Prime_Count = 42;
   end loop;
end Main;
</syntaxhighlight>
{{output}}
<pre>
n =  1                    43.0
n =  2                    89.0
n =  3                   179.0
n =  4                   359.0
n =  5                   719.0
n =  6                 1,439.0
n =  7                 2,879.0
n =  8                 5,779.0
n =  9                11,579.0
n = 10                23,159.0
n = 11                46,327.0
n = 12                92,657.0
n = 13               185,323.0
n = 14               370,661.0
n = 15               741,337.0
n = 16             1,482,707.0
n = 17             2,965,421.0
n = 18             5,930,887.0
n = 19            11,861,791.0
n = 20            23,723,597.0
n = 21            47,447,201.0
n = 22            94,894,427.0
n = 23           189,788,857.0
n = 24           379,577,741.0
n = 25           759,155,483.0
n = 26         1,518,310,967.0
n = 27         3,036,621,941.0
n = 28         6,073,243,889.0
n = 29        12,146,487,779.0
n = 30        24,292,975,649.0
n = 31        48,585,951,311.0
n = 32        97,171,902,629.0
n = 33       194,343,805,267.0
n = 34       388,687,610,539.0
n = 35       777,375,221,081.0
n = 36     1,554,750,442,183.0
n = 37     3,109,500,884,389.0
n = 38     6,219,001,768,781.0
n = 39    12,438,003,537,571.0
n = 40    24,876,007,075,181.0
n = 41    49,752,014,150,467.0
n = 42    99,504,028,301,131.0
</pre>

=={{header|ALGOL 68}}==
In Algol 68, the FOR loop counter cannot be modified in the loop. This uses a WHILE loop testing at the top but is otherwise largely a translation of the Kotlin entry.
<syntaxhighlight lang="algol68">BEGIN
    # returns TRUE if n is prime, FALSE otherwise #
    PROC is prime = ( LONG INT n )BOOL:
         IF   n MOD 2 = 0 THEN n = 2
         ELIF n MOD 3 = 0 THEN n = 3
         ELSE
            LONG INT d := 5;
            BOOL result := TRUE;
            WHILE IF   d * d > n   THEN FALSE
                  ELIF n MOD d = 0 THEN result := FALSE
                  ELIF d +:= 2;
                       n MOD d = 0 THEN result := FALSE
                  ELSE d +:= 4; TRUE
                  FI
            DO SKIP OD;
            result
         FI # is prime # ;

    LONG INT i := 42;
    LONG INT n := 0;
    WHILE n < 42 DO
        IF is prime( i ) THEN
            n +:= 1;
            print( ( "n = "
                   , whole( n,  -2 )
                   , "  "
                   , whole( i, -19 )
                   , newline
                   )
                 );
            i +:= i - 1
        FI;
        i +:= 1
    OD
END</syntaxhighlight>
{{out}}
<pre>
n =  1                   43
n =  2                   89
n =  3                  179
n =  4                  359
n =  5                  719
n =  6                 1439
n =  7                 2879
n =  8                 5779
n =  9                11579
n = 10                23159
n = 11                46327
n = 12                92657
n = 13               185323
n = 14               370661
n = 15               741337
n = 16              1482707
n = 17              2965421
n = 18              5930887
n = 19             11861791
n = 20             23723597
n = 21             47447201
n = 22             94894427
n = 23            189788857
n = 24            379577741
n = 25            759155483
n = 26           1518310967
n = 27           3036621941
n = 28           6073243889
n = 29          12146487779
n = 30          24292975649
n = 31          48585951311
n = 32          97171902629
n = 33         194343805267
n = 34         388687610539
n = 35         777375221081
n = 36        1554750442183
n = 37        3109500884389
n = 38        6219001768781
n = 39       12438003537571
n = 40       24876007075181
n = 41       49752014150467
n = 42       99504028301131
</pre>

=={{header|ARM Assembly}}==
{{works with|as|Raspberry Pi}}
<syntaxhighlight lang="arm assembly">
/* ARM assembly Raspberry PI  */
/*  program loopinc96.s   */
 
/************************************/
/* Constantes                       */
/************************************/
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ WRITE,  4     @ Linux syscall

/*********************************/
/* Initialized data              */
/*********************************/
.data
szMessMultOver:     .asciz "Multiplication 64 : Dépassement de capacité.\n"
sMessResult:        .ascii "Index  : "
sMessIndex:         .fill 11, 1, ' '            @ size => 11
                    .ascii "Value  : "
sMessValeur:        .fill 21, 1, ' '            @ size => 21
szCarriageReturn:   .asciz "\n"

/*********************************/
/* UnInitialized data            */
/*********************************/
.bss  
/*********************************/
/*  code section                 */
/*********************************/
.text
.global main 
main:                                              @ entry of program 
    mov r7,#0                                      @ counter
    mov r5,#42                                     @ start index low bits
    mov r6,#0                                      @ start index high bits
1:                                                 @ begin loop
    mov r0,r5
    mov r1,r6
    bl isPrime                                     @ prime ?
    bcs 100f                                       @ error overflow ?
    cmp r0,#1                                      @ is prime ?
    beq 2f                                         @ yes
    adds r5,#1                                     @ no -> increment index
    addcs r6,#1
    b 1b                                           @ and loop
2:                                                 @ display index and prime
    add r7,#1                                      @ increment counter
    mov r0,r7
    ldr r1,iAdrsMessIndex                          @ conversion index
    bl conversion10
    mov r0,r5
    mov r1,r6                                      @ conversion value
    ldr r2,iAdrsMessValeur
    bl conversionRegDoubleU                        @ conversion double -> ascii
    ldr r0,iAdrsMessResult
    bl affichageMess  
    
    adds r5,r5
    add r6,r6
    addcs r6,#1
    cmp r7,#42                                     @ end ?
    blt 1b                                         @ no loop

100:                                               @ standard end of the program 
    mov r0, #0                                     @ return code
    mov r7, #EXIT                                  @ request to exit program
    svc #0                                         @ perform the system call
 
iAdrsMessIndex:           .int sMessIndex
iAdrsMessValeur:          .int sMessValeur
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrsMessResult:          .int sMessResult


/******************************************************************/
/*     display text with size calculation                         */ 
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
    push {r0,r1,r2,r7,lr}                          @ save  registres
    mov r2,#0                                      @ counter length 
1:                                                 @ loop length calculation 
    ldrb r1,[r0,r2]                                @ read octet start position + index 
    cmp r1,#0                                      @ if 0 its over 
    addne r2,r2,#1                                 @ else add 1 in the length 
    bne 1b                                         @ and loop 
                                                   @ so here r2 contains the length of the message 
    mov r1,r0                                      @ address message in r1 
    mov r0,#STDOUT                                 @ code to write to the standard output Linux 
    mov r7, #WRITE                                 @ code call system "write" 
    svc #0                                         @ call systeme 
    pop {r0,r1,r2,r7,lr}                           @ restaur des  2 registres */ 
    bx lr                                          @ return  
/******************************************************************/
/*     Converting a register to a decimal unsigned                */ 
/******************************************************************/
/* r0 contains value and r1 address area   */
/* r0 return size of result (no zero final in area) */
/* area size => 11 bytes          */
.equ LGZONECAL,   10
conversion10:
    push {r1-r4,lr}                                   @ save registers 
    mov r3,r1
    mov r2,#LGZONECAL
1:                                                    @ start loop
    bl divisionpar10U                                 @ unsigned  r0 <- dividende. quotient ->r0 reste -> r1
    add r1,#48                                        @ digit
    strb r1,[r3,r2]                                   @ store digit on area
    cmp r0,#0                                         @ stop if quotient = 0 
    subne r2,#1                                       @ else previous position
    bne 1b                                            @ and loop
                                                      @ and move digit from left of area
    mov r4,#0
2:
    ldrb r1,[r3,r2]
    strb r1,[r3,r4]
    add r2,#1
    add r4,#1
    cmp r2,#LGZONECAL
    ble 2b
                                                      @ and move spaces in end on area
    mov r0,r4                                         @ result length 
    mov r1,#' '                                       @ space
3:
    strb r1,[r3,r4]                                   @ store space in area
    add r4,#1                                         @ next position
    cmp r4,#LGZONECAL
    ble 3b                                            @ loop if r4 <= area size
 
100:
    pop {r1-r4,lr}                                    @ restaur registres 
    bx lr                                             @return
 
/***************************************************/
/*   division par 10   unsigned                    */
/***************************************************/
/* r0 dividende   */
/* r0 quotient   */	
/* r1 remainder  */
divisionpar10U:
    push {r2,r3,r4, lr}
    mov r4,r0                                          @ save value
    //mov r3,#0xCCCD                                   @ r3 <- magic_number lower  raspberry 3
    //movt r3,#0xCCCC                                  @ r3 <- magic_number higter raspberry 3
    ldr r3,iMagicNumber                                @ r3 <- magic_number    raspberry 1 2
    umull r1, r2, r3, r0                               @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0) 
    mov r0, r2, LSR #3                                 @ r2 <- r2 >> shift 3
    add r2,r0,r0, lsl #2                               @ r2 <- r0 * 5 
    sub r1,r4,r2, lsl #1                               @ r1 <- r4 - (r2 * 2)  = r4 - (r0 * 10)
    pop {r2,r3,r4,lr}
    bx lr                                              @ leave function 
iMagicNumber:  	.int 0xCCCCCCCD
/***************************************************/
/*   number is prime ?              */
/***************************************************/
/* r0 contains low bytes of double */
/* r1 contains high bytes of double */
/* r0 returns 1 if prime else 0  */
@2147483647
@4294967297
@131071
isPrime:
    push {r1-r5,lr}                      @ save registers
    mov r4,r0                            @ save double
    mov r5,r1  
    subs r2,r0,#1                        @ exposant n - 1
    sbcs r3,r1,#0

    mov r0,#2                            @ base  2
    mov r1,#0
    bl moduloPuR96                       @ compute modulo
    bcs 100f                             @ overflow error
    cmp r0,#1                            @ modulo <> 1 -> no prime
    bne 90f 

    mov r0,#3                            @ base 3
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f
 
    mov r0,#5                            @ base 5
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f

    mov r0,#7                            @ base 7
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f

    mov r0,#11                           @ base 11
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f

    mov r0,#13                           @ base 13
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f

    mov r0,#17                           @ base 17
    mov r1,#0
    bl moduloPuR96
    bcs 100f                             @ overflow error
    cmp r0,#1
    bne 90f
    mov r0,#1                            @ is prime
    msr     cpsr_f, #0                   @ no error overflow zero -> flags
    b 100f
90:
    mov r0,#0                            @ no prime
    msr     cpsr_f, #0                   @ no error overflow zero -> flags
100:                                     @ fin standard de la fonction 
    pop {r1-r5,lr}                       @ restaur registers
    bx lr                                @ return 


/********************************************************/
/*   compute  b pow e modulo m  */
/*                                             */
/********************************************************/
/* r0 base double low bits */
/* r1 base double high bits */
/* r2 exposant low bitss  */
/* r3 exposant high bits */
/* r4 modulo low bits */
/* r5 modulo high bits */
/* r0 returns result low bits */
/* r1 returns result high bits */
/* if overflow , flag carry is set else is clear */
moduloPuR96:
    push {r2-r12,lr}                       @ save registers  
    cmp r0,#0                              @ control low byte <> zero 
    bne 1f
    cmp r1,#0                              @ control high bytes <> zero
    beq 100f
1:
    mov r9,r4                              @ modulo PB
    mov r10,r5                             @ modulo PH
    mov r5,r2                              @ exposant **
    mov r6,r3                              @ exposant
    mov r7,r0                              @ base PB
    mov r8,r1                              @ base PH
    mov r2,#0
    mov r3,r9
    mov r4,r10
    mov r11,#1                             @ result PB
    mov r12,#0                             @ result PH
/* r0 contient partie basse dividende */
/* r1 contient partie moyenne dividende */
/* r2 contient partie haute du diviseur */
/* r3 contient partie basse diviseur  */
/* r4 contient partie haute diviseur  */
/* r0 retourne partie basse du quotient */
/* r1 retourne partie moyenne du quotient */
/* r2 retourne partie haute du quotient */
/* r3 retourne partie basse du reste */
/* r4 retourne partie haute du reste */
    bl divisionReg96DU
    mov r7,r3                               @ base <- remainder
    mov r8,r4
2:
    tst r5,#1                               @ test du bit 0
    beq 3f
    mov r0,r7
    mov r1,r8
    mov r2,r11
    mov r3,r12
    bl multiplicationR96U
    bcs 100f                                @ error overflow
    mov r3,r9
    mov r4,r10
    bl divisionReg96DU
    mov r11,r3                              @ result <- remainder
    mov r12,r4
3:
    mov r0,r7
    mov r1,r8
    mov r2,r7
    mov r3,r8
    bl multiplicationR96U
    bcs 100f                                @ error overflow
    mov r3,r9
    mov r4,r10
    bl divisionReg96DU
    mov r7,r3                               @ base <- remainder
    mov r8,r4

    lsr r5,#1   
    lsrs r6,#1
    orrcs r5,#0x80000000
    cmp r5,#0
    bne 2b
    cmp r6,#0
    bne 2b
    mov r0,r11
    mov r1,r12
    msr     cpsr_f, #0                       @ no error overflow zero -> flags
100:                                         @ end function
   	pop {r2-r12,lr}                          @ restaur registers
    bx lr                                    @ return
/***************************************************/
/*   multiplication 2 registers (64 bits) unsigned */
/*   result in 3 registers 96 bits                 */
/***************************************************/
/* r0 low bits number 1    */
/* r1 high bits number 1    */
/* r2 low bits number 2    */
/* r3 high bits number 2    */
/* r0 returns low bits résult   */
/* r1 returns median bits résult */
/* r2 returns high bits résult  */
/* if overflow , flag carry is set else is clear */
multiplicationR96U:
    push {r3-r8,lr}           @ save registers
    umull r5,r6,r0,r2         @ mult low bits
    umull r4,r8,r0,r3         @ mult low bits 1 high bits 2
    mov r0,r5                 @ result low bits ok
    adds r4,r6                @ add results
    addcs  r8,#1              @ carry
    umull r6,r7,r1,r2         @ mult high bits 1 low bits 2
    adds r4,r6                @ add results
    addcs  r8,#1              @ carry 
    adds r8,r7                @ add results
    bcs 99f                   @ overflow ?
    umull r6,r7,r1,r3         @ mult high bits 1 high bits 2
    cmp r7,#0                 @ error overflow ?
    bne 99f   
    adds r8,r6                @ add results
    bcs 99f                   @ error overflow
    mov r1,r4                 @ return median bytes
    mov r2,r8                 @ return high bytes
    msr cpsr_f, #0            @ no error overflow zero -> flags
    b 100f
99:                           @ display message overflow
	ldr r0,iAdrszMessMultOver @
	bl affichageMess
    mov r0,#0
    mov r1,#0 
    msr cpsr_f, #1<<29        @ maj flag carry à 1  et tous les autres à 0
100:                          @ end function  
   	pop {r3-r8,lr}            @ restaur registers
    bx lr                     @ return 
iAdrszMessMultOver:         .int szMessMultOver
/***************************************************/
/*   division number (3 registers) 92 bits by number (2 registers) 64 bits */
/*           unsigned                            */
/***************************************************/
/* r0 low bits dividende */
/* r1 median bits dividende */
/* r2 high bits dividende */
/* r3 low bits divisor  */
/* r4 high bits divis0r  */
/* r0 returns low bits quotient */
/* r1 returns median bits quotient */
/* r2 returns high bits quotien */
/* r3 returns low bits remainder */
/* r4 returns high bits remainder */
/* remainder do not is 3 registers */
divisionReg96DU:
    push {r5-r10,lr}    @ save registers
    mov r7,r3           @ low bits divisor
    mov r8,r4           @ high bits divisor
    mov r4,r0           @ low bits dividende -> low bits quotient
    mov r5,r1           @ median bits dividende  -> median bits quotient
    mov r6,r2           @ high bits dividende -> high bits quotient

                        @ 
    mov r0,#0           @ low bits remainder
    mov r1,#0           @ median bits remainder
    mov r2,#0           @ high bits remainder (not useful)
    mov r9,#96          @ counter loop (32 bits * 3)
    mov r10,#0          @ last bit
1:
    lsl   r2,#1         @ shift left high bits remainder
    lsls  r1,#1         @ shift left median bits remainder
    orrcs r2,#1         @ left bit median -> right bit high
    lsls r0,#1          @ shift left low bits remainder
    orrcs r1,#1         @ left bit low -> right bit median
    lsls r6,#1          @ shift left high bits quotient
    orrcs r0,#1         @ left bit high -> right bit low remainder
    lsls r5,#1          @ shift left median bits quotient
    orrcs r6,#1         @ left bit median -> right bit high
    lsls r4,#1          @ shift left low bits quotient
    orrcs r5,#1         @ left bit low -> right bit median
    orr r4,r10          @ last bit -> bit 0 quotient
    mov r10,#0          @ raz du bit
                        @ compare  remainder and divisor
    cmp r2,#0           @ high bit remainder
    bne 2f
    cmp r1,r8           @ compare median bits 
    blo 3f              @ lower
    bhi 2f              @ highter
    cmp r0,r7           @ equal -> compare low bits
    blo 3f              @ lower
2:                      @ remainder > divisor
    subs r0,r7          @ sub divisor of remainder
    sbcs r1,r8
    mov r10,#0          @ reuse ponctuelle  r10
    sbc r2,r2,r10       @ carry 
    mov r10,#1          @ last bit à 1
3:
    subs r9,#1          @ increment counter loop
    bgt 1b              @ and loop
    lsl r6,#1           @ shift left high bits quotient
    lsls r5,#1          @ shift left median bits quotient
    orrcs r6,#1         @ left bit median -> right bit high
    lsls r4,#1          @ shift left low bits quotient
    orrcs r5,#1         @ left bit low -> right bit median
    orr r4,r10          @ last bit -> bit 0 quotient
    mov r3,r0           @ low bits remainder
    mov r0,r4           @ low bits quotient
    mov r4,r1           @ high bits remainder
    mov r1,r5           @ median bits quotient
    //mov r5,r2
    mov r2,r6           @ high bits quotient

100:                    @ end function  
   	pop {r5-r10,lr}     @ restaur registers
    bx lr               @ return 

/***************************************************/
/*   Conversion double integer 64bits in ascii     */
/***************************************************/
/* r0 contains low bits     */
/* r1 contains high bits    */
/* r2 contains address area */
conversionRegDoubleU:
    push {r0-r5,lr}         @ save registers
    mov r5,r2
    mov r4,#19              @ start location
    mov r2,#10              @ conversion decimale 
1:                          @ begin loop 
    bl divisionReg64U       @ division by 10
    add r3,#48              @ -> digit ascii
    strb r3,[r5,r4]         @ store digit in area index r4
    sub r4,r4,#1            @ decrement index
    cmp r0,#0               @ low bits quotient = zero ?
    bne 1b	                @ no -> loop
    cmp r1,#0               @ high bits quotient = zero ? 
    bne 1b                  @ no -> loop
                            @ spaces -> begin area 
    mov r3,#' '             @ space
2:
    strb r3,[r5,r4]         @ store space in area 
    subs r4,r4,#1           @ decrement index
    bge 2b                  @ and loop if > zéro 

100:                        @ end fonction  
   	pop {r0-r5,lr}          @ restaur registers
    bx lr                   @ return
/***************************************************/
/*   division number 64 bits / number 32 bits      */
/***************************************************/
/* r0 contains low bits dividende  */
/* r1 contains high bits dividente */
/* r2 contains divisor             */
/* r0 returns low bits quotient    */
/* r1 returns high bits quotient   */
/* r3 returns remainder            */
divisionReg64U:
    push {r4,r5,lr}    @ save registers
    mov r5,#0          @ raz remainder R
    mov r3,#64         @ loop counter
    mov r4,#0          @ last bit
1:
    lsl r5,#1          @ shift left remainder one bit
    lsls r1,#1         @ shift left high bits quotient one bit
    orrcs r5,#1        @ and bit -> remainder
    lsls r0,#1         @ shift left low bits quotient one bit
    orrcs r1,#1        @ and left bit -> high bits 
    orr r0,r4          @ last bit  quotient
    mov r4,#0          @ raz last bit
    cmp r5,r2          @ compare remainder divisor
    subhs r5,r2        @ if highter sub divisor of remainder
    movhs r4,#1        @  and 1 -> last bit
3:
    subs r3,#1         @ decrement counter loop
    bgt 1b             @ and loop if not zero
    lsl r1,#1          @ else shift left higt bits quotient
    lsls r0,#1         @ and shift  left low bits  
    orrcs r1,#1
    orr r0,r4          @ last bit quotient
    mov r3,r5
100:                   @ end function
    pop {r4,r5,lr}     @ restaur registers
    bx lr              @ return
</syntaxhighlight>
{{out}}
<Pre>
pi@raspberrypi:~/asm/rosetta/ASS3 $ loopsinc96
Index  : 1          Value  :                   43
Index  : 2          Value  :                   89
Index  : 3          Value  :                  179
Index  : 4          Value  :                  359
Index  : 5          Value  :                  719
Index  : 6          Value  :                 1439
Index  : 7          Value  :                 2879
Index  : 8          Value  :                 5779
Index  : 9          Value  :                11579
Index  : 10         Value  :                23159
Index  : 11         Value  :                46327
Index  : 12         Value  :                92657
Index  : 13         Value  :               185323
Index  : 14         Value  :               370661
Index  : 15         Value  :               741337
Index  : 16         Value  :              1482707
Index  : 17         Value  :              2965421
Index  : 18         Value  :              5930887
Index  : 19         Value  :             11861791
Index  : 20         Value  :             23723597
Index  : 21         Value  :             47447201
Index  : 22         Value  :             94894427
Index  : 23         Value  :            189788857
Index  : 24         Value  :            379577741
Index  : 25         Value  :            759155483
Index  : 26         Value  :           1518310967
Index  : 27         Value  :           3036621941
Index  : 28         Value  :           6073243889
Index  : 29         Value  :          12146487779
Index  : 30         Value  :          24292975649
Index  : 31         Value  :          48585951311
Index  : 32         Value  :          97171902629
Index  : 33         Value  :         194343805267
Index  : 34         Value  :         388687610539
Index  : 35         Value  :         777375221081
Index  : 36         Value  :        1554750442183
Index  : 37         Value  :        3109500884389
Index  : 38         Value  :        6219001768781
Index  : 39         Value  :       12438003537571
Index  : 40         Value  :       24876007075181
Index  : 41         Value  :       49752014150467
Index  : 42         Value  :       99504028301131
</pre>

=={{header|Arturo}}==
{{trans|Python}}
<syntaxhighlight lang="rebol">i: 42
n: 0

while [n<42][
	if? prime? i [
		n: n+1
		print ["n =" pad to :string n 2 pad to :string i 20]
		i: i + i
	]
	else [
		i: i + 1
	]
]</syntaxhighlight>
{{out}}
<pre>n =  1                   43 
n =  2                   89 
n =  3                  179 
n =  4                  359 
n =  5                  719 
n =  6                 1439 
n =  7                 2879 
n =  8                 5779 
n =  9                11579 
n = 10                23159 
n = 11                46327 
n = 12                92657 
n = 13               185323 
n = 14               370661 
n = 15               741337 
n = 16              1482707 
n = 17              2965421 
n = 18              5930887 
n = 19             11861791 
n = 20             23723597 
n = 21             47447201 
n = 22             94894427 
n = 23            189788857 
n = 24            379577741 
n = 25            759155483 
n = 26           1518310967 
n = 27           3036621941 
n = 28           6073243889 
n = 29          12146487779 
n = 30          24292975649 
n = 31          48585951311 
n = 32          97171902629 
n = 33         194343805267 
n = 34         388687610539 
n = 35         777375221081 
n = 36        1554750442183 
n = 37        3109500884389 
n = 38        6219001768781 
n = 39       12438003537571 
n = 40       24876007075181 
n = 41       49752014150467 
n = 42       99504028301131</pre>

=={{header|AutoHotkey}}==
<syntaxhighlight lang="autohotkey">i:= 42, n:= 1, result := ""
while (n<43){
	if isPrime(i)
		result .= n ":`t" RegExReplace(i, "\B(?=(\d{3})+$)", ",") "`n", i*=2, n++
	else 
		i++
}
MsgBox, 262208, , % result
return

isPrime(num){
	if !Mod(num, 2) || !Mod(num, 3) 
		return false
	lim := Sqrt(num),	i := 5
	while (i<lim){
		if !Mod(num, i)
			return false
		i+=2
	}
	return true
}</syntaxhighlight>
{{out}}
<pre>1:	43
2:	89
3:	179
4:	359
5:	719
6:	1,439
7:	2,879
8:	5,779
9:	11,579
10:	23,159
11:	46,327
12:	92,657
13:	185,323
14:	370,661
15:	741,337
16:	1,482,707
17:	2,965,421
18:	5,930,887
19:	11,861,791
20:	23,723,597
21:	47,447,201
22:	94,894,427
23:	189,788,857
24:	379,577,741
25:	759,155,483
26:	1,518,310,967
27:	3,036,621,941
28:	6,073,243,889
29:	12,146,487,779
30:	24,292,975,649
31:	48,585,951,311
32:	97,171,902,629
33:	194,343,805,267
34:	388,687,610,539
35:	777,375,221,081
36:	1,554,750,442,183
37:	3,109,500,884,389
38:	6,219,001,768,781
39:	12,438,003,537,571
40:	24,876,007,075,181
41:	49,752,014,150,467
42:	99,504,028,301,131</pre>

=={{header|AWK}}==
<syntaxhighlight lang="awk">
# syntax: GAWK -f LOOPS_INCREMENT_LOOP_INDEX_WITHIN_LOOP_BODY.AWK
BEGIN {
    limit = 42
    n = 0
    for (i=limit; n<limit; i++) {
      if (is_prime(i)) {
        printf("%2d %19'd\n",++n,i)
        i += i - 1
      }
    }
    exit(0)
}
function is_prime(n,  d) {
    if (n % 2 == 0) { return(n == 2) }
    if (n % 3 == 0) { return(n == 3) }
    d = 5
    while (d*d <= n) {
      if (n % d == 0) { return(0) }
      d += 2
      if (n % d == 0) { return(0) }
      d += 4
    }
    return(1)
}
</syntaxhighlight>
{{out}}
<pre>
 1                  43
 2                  89
 3                 179
 4                 359
 5                 719
 6               1,439
 7               2,879
 8               5,779
 9              11,579
10              23,159
11              46,327
12              92,657
13             185,323
14             370,661
15             741,337
16           1,482,707
17           2,965,421
18           5,930,887
19          11,861,791
20          23,723,597
21          47,447,201
22          94,894,427
23         189,788,857
24         379,577,741
25         759,155,483
26       1,518,310,967
27       3,036,621,941
28       6,073,243,889
29      12,146,487,779
30      24,292,975,649
31      48,585,951,311
32      97,171,902,629
33     194,343,805,267
34     388,687,610,539
35     777,375,221,081
36   1,554,750,442,183
37   3,109,500,884,389
38   6,219,001,768,781
39  12,438,003,537,571
40  24,876,007,075,181
41  49,752,014,150,467
42  99,504,028,301,131
</pre>


=={{header|BASIC256}}==
<syntaxhighlight lang="basic256">function isPrime(number)
	if (number % 2 = 0) or (number % 3 = 0) then return false
	lim = sqr(number)

	for i = 5 to lim step 2
		if number % i = 0 then return false
	next i

	return true
end function

i = 42
counter = 0
while counter < 42
	if isPrime(i) then
		counter += 1
		print "n = "; counter, i
		i += i - 1
	end if
	i += 1
end while
end</syntaxhighlight>


=={{header|C}}==
The following uses a 'for' rather than a 'do/while' loop but otherwise is similar to the Kotlin
entry. 

The 'thousands separator' aspect (using the ' flag in printf and setting the locale appropriately) works fine when compiled with gcc on Ubuntu 14.04 but may not work on some other systems as this is not a standard flag.
<syntaxhighlight lang="c">#include <stdio.h>
#include <locale.h>

#define LIMIT 42

int is_prime(long long n) {
    if (n % 2 == 0) return n == 2;
    if (n % 3 == 0) return n == 3;
    long long d = 5;
    while (d * d <= n) {
        if (n % d == 0) return 0;
        d += 2;
        if (n % d == 0) return 0;
        d += 4;
    }
    return 1;
}

int main() {
    long long i;
    int n;
    setlocale(LC_NUMERIC, "");
    for (i = LIMIT, n = 0; n < LIMIT; i++)
        if (is_prime(i)) {
            n++;
            printf("n = %-2d  %'19lld\n", n, i);
            i += i - 1;
        }
    return 0;
}</syntaxhighlight>

{{out}}
<pre>
Same as Kotlin entry
</pre>

=={{header|C sharp|C#}}==
<syntaxhighlight lang="csharp">
using System;
using System.Globalization;

namespace PrimeNumberLoopcs
{
    class Program
    {
        static bool isPrime(double number)
        {
            for(double i = number - 1; i > 1; i--)
            {
                if (number % i == 0)
                    return false;
            }
            return true;
        }
        static void Main(string[] args)
        {
            NumberFormatInfo nfi = new CultureInfo("en-US", false).NumberFormat;
            nfi.NumberDecimalDigits = 0;
            double i = 42;
            int n = 0;
            while (n < 42)
            {
                if (isPrime(i))
                {
                    n++;
                    Console.WriteLine("n = {0,-20} {1,20}", n, i.ToString("N", nfi));
                    i += i - 1;
                }
                i++;
            }
        }
    }
}</syntaxhighlight>
{{out}}
<pre>
n = 1                                      43
n = 2                                      89
n = 3                                     179
n = 4                                     359
n = 5                                     719
n = 6                                   1,439
n = 7                                   2,879
n = 8                                   5,779
n = 9                                  11,579
n = 10                                 23,159
n = 11                                 46,327
n = 12                                 92,657
n = 13                                185,323
n = 14                                370,661
n = 15                                741,337
n = 16                              1,482,707
n = 17                              2,965,421
n = 18                              5,930,887
n = 19                             11,861,791
n = 20                             23,723,597
n = 21                             47,447,201
n = 22                             94,894,427
n = 23                            189,788,857
n = 24                            379,577,741
n = 25                            759,155,483
n = 26                          1,518,310,967
n = 27                          3,036,621,941
n = 28                          6,073,243,889
n = 29                         12,146,487,779
n = 30                         24,292,975,649
n = 31                         48,585,951,311
n = 32                         97,171,902,629
n = 33                        194,343,805,267
n = 34                        388,687,610,539
n = 35                        777,375,221,081
n = 36                      1,554,750,442,183
n = 37                      3,109,500,884,389
n = 38                      6,219,001,768,781
n = 39                     12,438,003,537,571
n = 40                     24,876,007,075,181
n = 41                     49,752,014,150,467
n = 42                     99,504,028,301,131
</pre>

=={{header|C++}}==
<syntaxhighlight lang="cpp">
#include "stdafx.h"
#include <iostream>
#include <math.h> 
using namespace std;

bool isPrime(double number)
{    
    for (double i = number - 1; i >= 2; i--) {
        if (fmod(number, i) == 0)
	    return false;
    }
    return true;
}
int main()
{
    double i = 42;
    int n = 0;
    while (n < 42)
    {
        if (isPrime(i))
        {
            n++;
	    cout.width(1); cout << left << "n = " << n;
            //Only for Text Alignment
            if (n < 10)
	    {
	        cout.width(40); cout << right << i << endl;
	    }
	    else
	    {
		cout.width(39); cout << right << i << endl;
	    }
            i += i - 1;
	}
	i++;
    }
    return 0;
}</syntaxhighlight>

=={{header|Common Lisp}}==
<syntaxhighlight lang="lisp">
(defun primep (n)                            ; https://stackoverflow.com/questions/15817350/
  (cond ((= 2 n) t)                          ; Hard-code "2 is a prime"
        ((= 3 n) t)                          ; Hard-code "3 is a prime"
        ((evenp n) nil)                      ; If we're looking at an even now, it's not a prime
        (t                                   ; If it is divisible by an odd number below its square root, it's not prime
	 (do* ((i 3 (incf i 2)))             ; Initialize to 3 and increment by 2 on every loop
	      ((or (> i (isqrt n))           ; Break condition index exceeds its square root
		   (zerop (mod n i)))        ; Break condition it is divisible
	       (not (zerop (mod n i))))))))  ; Returns not divisible, aka prime

(do ((i 42)                                  ; Initialize index to 42
     (c 0))                                  ; Initialize count of primes to 0
    ((= c 42))                               ; Break condition when there are 42 primes
  (incf i)                                   ; Increments index by unity
  (if (primep i)(progn (incf c)              ; If prime increment count of primes
		       (format t "~&~5<~d~;->~>~20<~:d~>" c i) ; Display count of primes found and the prime
		       (incf i (decf i)))))  ; Increment index to previous index plus the prime
</syntaxhighlight>
{{out}}
<pre>
1  ->                  43
2  ->                  89
3  ->                 179
4  ->                 359
5  ->                 719
6  ->               1,439
7  ->               2,879
8  ->               5,779
9  ->              11,579
10 ->              23,159
11 ->              46,327
12 ->              92,657
13 ->             185,323
14 ->             370,661
15 ->             741,337
16 ->           1,482,707
17 ->           2,965,421
18 ->           5,930,887
19 ->          11,861,791
20 ->          23,723,597
21 ->          47,447,201
22 ->          94,894,427
23 ->         189,788,857
24 ->         379,577,741
25 ->         759,155,483
26 ->       1,518,310,967
27 ->       3,036,621,941
28 ->       6,073,243,889
29 ->      12,146,487,779
30 ->      24,292,975,649
31 ->      48,585,951,311
32 ->      97,171,902,629
33 ->     194,343,805,267
34 ->     388,687,610,539
35 ->     777,375,221,081
36 ->   1,554,750,442,183
37 ->   3,109,500,884,389
38 ->   6,219,001,768,781
39 ->  12,438,003,537,571
40 ->  24,876,007,075,181
41 ->  49,752,014,150,467
42 ->  99,504,028,301,131
</pre>
=={{header|Delphi}}==
{{libheader| System.SysUtils}}
{{Trans|C#}}
<syntaxhighlight lang="delphi">
program Increment_loop_index_within_loop_body;

{$APPTYPE CONSOLE}

uses
  System.SysUtils;

function IsPrime(const a: UInt64): Boolean;
var
  d: UInt64;
begin
  if (a < 2) then
    exit(False);

  if (a mod 2) = 0 then
    exit(a = 2);

  if (a mod 3) = 0 then
    exit(a = 3);

  d := 5;

  while (d * d <= a) do
  begin
    if (a mod d = 0) then
      Exit(false);
    inc(d, 2);

    if (a mod d = 0) then
      Exit(false);
    inc(d, 4);
  end;

  Result := True;
end;

var
  i, n: UInt64;

begin
  FormatSettings.ThousandSeparator:= ',';
  i := 42;
  n := 0;
  while (n < 42) do
  begin
    if (isPrime(i)) then
    begin
      inc(n);
      Writeln('n = ', n: -20, ' ', floattostrF(i, ffNumber, 20,0):20);
      i := 2 * i - 1;
    end;
    inc(i);
  end;
  readln;
end.</syntaxhighlight>
{{out}}
Same of [[#C#]].

=={{header|Dyalect}}==

<syntaxhighlight lang="dyalect">func isPrime(number) {
    if number <= 1 {
        return false
    }
    else if number % 2 == 0 {
        return number == 2
    }

    var i = 3

    while (i * i) < number {
        if number % i == 0 {
            return false
        }
        i += 2
    }

    return true
}

var i = 42
var n = 0

while n < 42 {
    if isPrime(i) {
        n += 1
        print("n = \(n)\t\(i)")
        i += i - 1
    }
    i += 1
}</syntaxhighlight>

Output:

<pre>n = 1   43
n = 2   89
n = 3   179
n = 4   359
n = 5   719
n = 6   1439
n = 7   2879
n = 8   5779
n = 9   11579
n = 10  23159
n = 11  46327
n = 12  92657
n = 13  185323
n = 14  370661
n = 15  741337
n = 16  1482707
n = 17  2965421
n = 18  5930887
n = 19  11861791
n = 20  23723597
n = 21  47447201
n = 22  94894427
n = 23  189788857
n = 24  379577741
n = 25  759155483
n = 26  1518310967
n = 27  3036621941
n = 28  6073243889
n = 29  12146487779
n = 30  24292975649
n = 31  48585951311
n = 32  97171902629
n = 33  194343805267
n = 34  388687610539
n = 35  777375221081
n = 36  1554750442183
n = 37  3109500884389
n = 38  6219001768781
n = 39  12438003537571
n = 40  24876007075181
n = 41  49752014150467
n = 42  99504028301131</pre>

=={{header|F_Sharp|F#}}==
This task uses [http://www.rosettacode.org/wiki/Extensible_prime_generator#The_function Extensible Prime Generator (F#)]
<syntaxhighlight lang="fsharp">
// Well I don't do loops. Nigel Galloway: March 17th., 2019. Let me try to explain where the loopy variables are, for the imperatively constrained.  
// cUL allows me to claim the rather trivial extra credit (commas in the numbers)
let cUL=let g=System.Globalization.CultureInfo("en-GB") in (fun (n:uint64)->n.ToString("N0",g))
// fN is primality by trial division
let fN g=pCache|>Seq.map uint64|>Seq.takeWhile(fun n->n*n<g)|>Seq.forall(fun n->g%n>0UL)
// unfold is sort of a loop incremented by 1 in this case
let fG n=Seq.unfold(fun n->Some(n,(n+1UL))) n|>Seq.find(fN)
// unfold is sort of a loop with fG as an internal loop incremented by the exit value of the internal loop in this case.
Seq.unfold(fun n->let n=fG n in Some(n,n+n)) 42UL|>Seq.take 42|>Seq.iteri(fun n g->printfn "%2d -> %s"  (n+1) (cUL g))
</syntaxhighlight>
{{out}}
<pre>
 1 -> 43
 2 -> 89
 3 -> 179
 4 -> 359
 5 -> 719
 6 -> 1,439
 7 -> 2,879
 8 -> 5,779
 9 -> 11,579
10 -> 23,159
11 -> 46,327
12 -> 92,657
13 -> 185,323
14 -> 370,661
15 -> 741,337
16 -> 1,482,707
17 -> 2,965,421
18 -> 5,930,887
19 -> 11,861,791
20 -> 23,723,597
21 -> 47,447,201
22 -> 94,894,427
23 -> 189,788,857
24 -> 379,577,741
25 -> 759,155,483
26 -> 1,518,310,967
27 -> 3,036,621,941
28 -> 6,073,243,889
29 -> 12,146,487,779
30 -> 24,292,975,649
31 -> 48,585,951,311
32 -> 97,171,902,629
33 -> 194,343,805,267
34 -> 388,687,610,539
35 -> 777,375,221,081
36 -> 1,554,750,442,183
37 -> 3,109,500,884,389
38 -> 6,219,001,768,781
39 -> 12,438,003,537,571
40 -> 24,876,007,075,181
41 -> 49,752,014,150,467
42 -> 99,504,028,301,131
</pre>

=={{header|Factor}}==
Explicit loop indices are non-idiomatic, but Factor is certainly capable of using them. Factor has a for loop near-equivalent, <code><range> [ ] each</code>, but since it doesn't mesh well with mutation, a while loop is used.
=== Using two numbers on the data stack ===
<syntaxhighlight lang="factor">USING: formatting kernel math math.primes
tools.memory.private ;
IN: rosetta-code.loops-inc-body

42
0
[ dup 42 < ] [
    over prime? [
        1 + 2dup swap commas
        "n = %-2d  %19s\n" printf
        [ dup + 1 - ] dip
    ] when
    [ 1 + ] dip
] while
2drop</syntaxhighlight>
=== Using lexical variables ===
Factor provides lexical variables for situations where they improve readability.
<syntaxhighlight lang="factor">USING: formatting kernel math math.primes
tools.memory.private ;
IN: rosetta-code.loops-inc-body

[let
    42 :> i!
    0  :> n!
    [ n 42 < ] [
        i prime? [
            n 1 + n!
            n i commas "n = %-2d  %19s\n" printf
            i i + 1 - i!
        ] when
        i 1 + i!
    ] while
]</syntaxhighlight>
{{out}}
<pre>
n = 1                    43
n = 2                    89
n = 3                   179
n = 4                   359
n = 5                   719
n = 6                 1,439
n = 7                 2,879
n = 8                 5,779
n = 9                11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131
</pre>

=={{header|Fortran}}==
Fortran does not allow to modify the index inside the loop.
<syntaxhighlight lang="fortran">do i=1,10
  write(*,*) i
  i=i+1
end do</syntaxhighlight>
<pre>
Error - I is currently being used as a DO or implied DO control variable
Compilation failed.
</pre>

===Fortran 95===
<syntaxhighlight lang="fortran">! Loops Increment loop index within loop body - 17/07/2018
      integer*8 n
      imax=42
      i=0; n=42
      Do While(i<imax)
        If (isprime(n)==1) Then
          i=i+1
          Write (*,'(I2,1X,I20)') i,n
          n=n+n-1
        EndIf
        n=n+1
      EndDo
      End

      Function isprime(n)
        integer*8 n,i
        If (n==2 .OR. n==3) Then
          isprime=1
          return
        ElseIf (Mod(n,2)==0 .OR. Mod(n,3)==0) Then
          isprime=0
          return
        Else
          i=5
          Do While(i*i<=n)
            If (Mod(n,i)==0 .OR. Mod(n,i+2)==0) Then
              isprime=0
              return
            EndIf
            i=i+6
          EndDo
          isprime=1
          return
        EndIf
      EndFunction</syntaxhighlight>
{{out}}
<pre style="height:60ex">
 1                   43
 2                   89
 3                  179
 4                  359
 5                  719
 6                 1439
 7                 2879
 8                 5779
 9                11579
10                23159
11                46327
12                92657
13               185323
14               370661
15               741337
16              1482707
17              2965421
18              5930887
19             11861791
20             23723597
21             47447201
22             94894427
23            189788857
24            379577741
25            759155483
26           1518310967
27           3036621941
28           6073243889
29          12146487779
30          24292975649
31          48585951311
32          97171902629
33         194343805267
34         388687610539
35         777375221081
36        1554750442183
37        3109500884389
38        6219001768781
39       12438003537571
40       24876007075181
41       49752014150467
42       99504028301131
</pre>

===Fortran IV===
The limit is set to 25 due to the size of integer in Fortran IV.
<syntaxhighlight lang="fortran">C LOOPS INCREMENT LOOP INDEX WITHIN LOOP BODY - 17/07/2018
      IMAX=25
      I=0
      N=42
  10  IF(I.GE.IMAX)GOTO 30
        IF(ISPRIME(N).NE.1)GOTO 20
          I=I+1
          WRITE(*,301) I,N
 301      FORMAT(I2,1X,I10)
          N=N+N-1
  20    N=N+1
      GOTO 10
  30  CONTINUE
      END

      FUNCTION ISPRIME(M)
        IF(M.NE.2 .AND. M.NE.3)GOTO 10
          ISPRIME=1
          RETURN
  10    IF(MOD(M,2).NE.0 .AND. MOD(M,3).NE.0)GOTO 20
          ISPRIME=0
          RETURN
  20      I=5
  30      IF(I*I.GT.M)GOTO 50
            IF(MOD(M,I).NE.0 .AND. MOD(M,I+2).NE.0)GOTO 40
              ISPRIME=0
              RETURN
  40        I=I+6
          GOTO 30 
  50      ISPRIME=1
          RETURN
      END</syntaxhighlight>
{{out}}
<pre style="height:60ex">
 1         43
 2         89
 3        179
 4        359
 5        719
 6       1439
 7       2879
 8       5779
 9      11579
10      23159
11      46327
12      92657
13     185323
14     370661
15     741337
16    1482707
17    2965421
18    5930887
19   11861791
20   23723597
21   47447201
22   94894427
23  189788857
24  379577741
25  759155483
</pre>

=={{header|FreeBASIC}}==
<syntaxhighlight lang="freebasic">' version 18-01-2019
' compile with: fbc -s console

Function isprime(number As ULongInt) As UInteger

    If number Mod 2 = 0 Then Return 0
    If number Mod 3 = 0 Then Return 0
    Dim As UInteger i, max = Sqr(number)

    For i = 5 To max Step 2
        If number Mod i = 0 Then Return 0
    Next

    Return 1

End Function

' ------=< MAIN >=------

Dim As UInteger counter
Dim As ULongInt i

Print : Print
counter = 0
For i = 42 To &HFFFFFFFFFFFFFFFF    ' for next loop, loop maximum = 2^64-1
    If isprime(i) Then
        counter += 1
        Print Using "n =### ##################,"; counter; i
        If counter >= 42 Then Exit for
        i += i -1
    End If
Next

' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End</syntaxhighlight>
{{out}}
<pre style="height:40ex">n =  1                  43
n =  2                  89
n =  3                 179
n =  4                 359
n =  5                 719
n =  6               1,439
n =  7               2,879
n =  8               5,779
n =  9              11,579
n = 10              23,159
n = 11              46,327
n = 12              92,657
n = 13             185,323
n = 14             370,661
n = 15             741,337
n = 16           1,482,707
n = 17           2,965,421
n = 18           5,930,887
n = 19          11,861,791
n = 20          23,723,597
n = 21          47,447,201
n = 22          94,894,427
n = 23         189,788,857
n = 24         379,577,741
n = 25         759,155,483
n = 26       1,518,310,967
n = 27       3,036,621,941
n = 28       6,073,243,889
n = 29      12,146,487,779
n = 30      24,292,975,649
n = 31      48,585,951,311
n = 32      97,171,902,629
n = 33     194,343,805,267
n = 34     388,687,610,539
n = 35     777,375,221,081
n = 36   1,554,750,442,183
n = 37   3,109,500,884,389
n = 38   6,219,001,768,781
n = 39  12,438,003,537,571
n = 40  24,876,007,075,181
n = 41  49,752,014,150,467
n = 42  99,504,028,301,131</pre>

=={{header|Go}}==
This uses Go's 'for' loop but is otherwise similar to the Kotlin entry.

The 'thousands separator' aspect is dealt with by a couple of external packages (in the 'import' declarations) which can be installed using 'go get'.
<syntaxhighlight lang="go">package main

import(
    "golang.org/x/text/language"
    "golang.org/x/text/message"
)

func isPrime(n uint64) bool {
    if n % 2 == 0 {
        return n == 2
    }
    if n % 3 == 0 {
        return n == 3
    }
    d := uint64(5)
    for d * d <= n {
        if n % d == 0 {
            return false
        }
        d += 2
        if n % d == 0 {
            return false
        } 
        d += 4
    }
    return true
}

const limit = 42

func main() {
    p := message.NewPrinter(language.English)
    for i, n := uint64(limit), 0; n < limit; i++ {
        if isPrime(i) {
            n++
            p.Printf("n = %-2d  %19d\n", n, i)
            i += i - 1
        }
    }
}</syntaxhighlight>

{{out}}
<pre>
Same as Kotlin entry
</pre>

=={{header|Haskell}}==
No index mutations or loops. Recursion is used.
<syntaxhighlight lang="haskell">import Data.List
import Control.Monad (guard)

isPrime :: Int -> Bool
isPrime n
  | n <= 3 = n > 1
  | n `mod` 2 == 0 || n `mod` 3 == 0 = False
  | otherwise = l2 5 n
  where l2 d n = x > n || l3 d n
          where x = d * d
                l3 d n
                  | n `mod` d == 0       = False
                  | n `mod` (d + 2) == 0 = False
                  | otherwise = l2 (d + 6) n

showPrime :: Int -> Int -> [(Int, Int)]
showPrime i n = if isPrime i
                then (n, i) : showPrime (i+i) (n+1)
                else showPrime (i+1) n

digitGroup :: Int -> String
digitGroup = intercalate "," . reverse . map show . unfoldr (\n -> guard (n /= 0) >> pure (n `mod` 1000, n `div` 1000))

display :: (Int, Int) -> String
display (i, p) = show i ++ " " ++ digitGroup p

main = mapM_ (putStrLn . display) $ take 42 $ showPrime 42 1</syntaxhighlight>
{{out}}
<pre>
1 43
2 89
3 179
4 359
5 719
6 1,439
7 2,879
8 5,779
9 11,579
10 23,159
11 46,327
12 92,657
13 185,323
14 370,661
15 741,337
16 1,482,707
17 2,965,421
18 5,930,887
19 11,861,791
20 23,723,597
21 47,447,201
22 94,894,427
23 189,788,857
24 379,577,741
25 759,155,483
26 1,518,310,967
27 3,36,621,941
28 6,73,243,889
29 12,146,487,779
30 24,292,975,649
31 48,585,951,311
32 97,171,902,629
33 194,343,805,267
34 388,687,610,539
35 777,375,221,81
36 1,554,750,442,183
37 3,109,500,884,389
38 6,219,1,768,781
39 12,438,3,537,571
40 24,876,7,75,181
41 49,752,14,150,467
42 99,504,28,301,131
</pre>

And for minor variation, we could import isPrime from Data.Numbers.Primes, and define the comma-grouping of large integers in terms of chunksof:

<syntaxhighlight lang="haskell">import Data.Numbers.Primes
import Data.List (intercalate)
import Data.List.Split (chunksOf)

series :: Integer -> Integer -> [(Integer, Integer)]
series = go
  where
    go i n
      | isPrime i = (n, i) : go (i + i) (succ n)
      | otherwise = go (succ i) n

showPair :: (Integer, Integer) -> String
showPair (i, n) = show i ++ " -> " ++ showInteger n

showInteger :: Integer -> String
showInteger = reverse . intercalate "," . chunksOf 3 . reverse . show

main :: IO ()
main = mapM_ (putStrLn . showPair) (take 42 $ series 42 1)</syntaxhighlight>

=={{header|Haxe}}==
Haxe's for-loop does allow the index to be modified in the body of the loop, so a while-loop is used instead.
<syntaxhighlight lang="haxe">using StringTools;
import haxe.Int64;

class PrimeNumberLoops {
  private static var limit = 42;
  
  static function isPrime(i:Int64):Bool {
    if (i == 2 || i == 3) {
      return true;
    } else if (i % 2 == 0 || i % 3 ==0) {
      return false;
    }
    var idx:haxe.Int64 = 5;
    while (idx * idx <= i) {
      if (i % idx == 0) return false;
      idx += 2;
      if (i % idx == 0) return false;
      idx += 4;
    }
    return true;
  }

  static function main() {
    var i:Int64 = 42;
    var n:Int64 = 0;
    while (n < limit) {
      if (isPrime(i)) {
        n++;
        Sys.println('n ${Int64.toStr(n).lpad(' ', 2)} ' +
                    '= ${Int64.toStr(i).lpad(' ', 19)}');
        i += i;
        continue;
      }
      i++;
    }
  }
}</syntaxhighlight>

{{out}}
<pre>
n  1 =                  43
n  2 =                  89
n  3 =                 179
n  4 =                 359
n  5 =                 719
n  6 =                1439
n  7 =                2879
n  8 =                5779
n  9 =               11579
n 10 =               23159
n 11 =               46327
n 12 =               92657
n 13 =              185323
n 14 =              370661
n 15 =              741337
n 16 =             1482707
n 17 =             2965421
n 18 =             5930887
n 19 =            11861791
n 20 =            23723597
n 21 =            47447201
n 22 =            94894427
n 23 =           189788857
n 24 =           379577741
n 25 =           759155483
n 26 =          1518310967
n 27 =          3036621941
n 28 =          6073243889
n 29 =         12146487779
n 30 =         24292975649
n 31 =         48585951311
n 32 =         97171902629
n 33 =        194343805267
n 34 =        388687610539
n 35 =        777375221081
n 36 =       1554750442183
n 37 =       3109500884389
n 38 =       6219001768781
n 39 =      12438003537571
n 40 =      24876007075181
n 41 =      49752014150467
n 42 =      99504028301131
</pre>

=={{header|J}}==
An idiomatic approach:
<syntaxhighlight lang=J>   (,.~#\)}:(}:, (,1&p: # _1 2&p.)@:>:@{:)^:(42 >: #)^:_ x: 42
 1             43
 2             89
 3            179
 4            359
 5            719
 6           1439
 7           2879
 8           5779
 9          11579
10          23159
11          46327
12          92657
13         185323
14         370661
15         741337
16        1482707
17        2965421
18        5930887
19       11861791
20       23723597
21       47447201
22       94894427
23      189788857
24      379577741
25      759155483
26     1518310967
27     3036621941
28     6073243889
29    12146487779
30    24292975649
31    48585951311
32    97171902629
33   194343805267
34   388687610539
35   777375221081
36  1554750442183
37  3109500884389
38  6219001768781
39 12438003537571
40 24876007075181
41 49752014150467
42 99504028301131
</syntaxhighlight>

Most of the remainder of this treatment ignores output formatting issues and focuses purely on algorithmic issues.

The loop index from J's <code>for.</code> is read only. But we can use a while loop to achieve the effect of a mutable loop index.

Here are some sketches, starting with that concept and developing some plausible alternative approaches:

A variant derived from the python solution (except this loop returns the list of computed values rather than displays them):
<syntaxhighlight lang="j">
isPrime =: 1&p:
assert 1 1 0 -: isPrime 2 3 4   NB. test and example

loop =: verb define
 i =. x: y
 n =. i. 0
 while. y > # n do.
  if. isPrime i do.
   n =. n , i
   i =. _1 2 p. i
  end.
  i =. i + 1
 end.
 n 
)
</syntaxhighlight>
Store the vector of indexes using its tail as the current index, removing the `n' variable.  In doing so the last item of `i' is not part of the solution, hence change less than to less or equal, and discard the tail value.  Also extract the conversion to extended precision x: .
<syntaxhighlight lang="j">
loop =: verb define@:x:
 i =. y
 while. y >: # i do.
  if. isPrime {: i do.
   i =. (, _1 2 p. {:) i
  end.
  i =. _1 (>:@:{)`[`]} i
 end.
 }: i
)
</syntaxhighlight>

Replace the "if" statement with a computation.  This one works by appending onto the solution vector isPrime copies of the proposed new index.
<syntaxhighlight lang="j">
loop =: verb define@:x:
 i =. y
 while. y >: # i do.
  i =. (, (isPrime # _1 2&p.)@:{:) i
  i =. _1 (>:@:{)`[`]} i
 end.
 }: i
)
</syntaxhighlight>
Names are an issue brought forth in the j forums.  Names have most meaning to the person who wrote them, so there's a bit of J philosophy that says "show the code".  J doesn't enforce "code only", and definitions can encapsulate useful chunks of code.  If the names I've chosen don't work in your experience or language you could replace them with `a' and `b'.
<syntaxhighlight lang="j">
save_if_prime =: , (isPrime # _1 2&p.)@:{:
increment_tail =: _1&(>:@:{`[`]})

loop =: verb define@:x:
 i =. y
 while. y >: # i do.
  i =. save_if_prime i
  i =. increment_tail i
 end.
 }: i
)
</syntaxhighlight>
Why make two assignments when j can increment at save?
<syntaxhighlight lang="j">
loop =: verb define@:x:
 i =. y
 while. y >: # i do.
  i =. increment_tail@:save_if_prime i
 end.
 }: i
)
</syntaxhighlight>
Next replace the while loop with double application of J's generalized power conjunction.
<syntaxhighlight lang="j">
While =: conjunction def 'u^:(0~:v)^:_'

loop =: verb define@:x:
 i =. y
 }: increment_tail@:save_if_prime While(y >: #) i
)
</syntaxhighlight>
By inspection the variable `i' doesn't contribute anything useful whatsoever.  The verb's argument, y, remains.
Finally, implemented as an hook [http://www.jsoftware.com/help/dictionary/dictf.htm verb trains] with 'y' and `i' as left ([) and right (]) arguments the complete definitions for tacit_loop are
<syntaxhighlight lang="j">
isPrime =: 1&p:
save_if_prime =: , (isPrime # _1 2&p.)@:{:
increment_tail =: _1&(>:@:{`[`]})
While =: conjunction def 'u^:(0~:v)^:_'
tacit_loop =: [: }: (increment_tail@:save_if_prime@:]While(>: #) x:)
</syntaxhighlight>
Include the index numbers with demonstration:
<syntaxhighlight lang="j">
   9!:37 ] 0 2048 0 222  NB. output control permit lines of 2^11 columns

   (>:@:i. ,: tacit_loop) 42
 1  2   3   4   5    6    7    8     9    10    11    12     13     14     15      16      17      18       19       20       21       22        23        24        25         26         27         28          29          30          31          32           33           34           35            36            37            38             39             40             41             42
43 89 179 359 719 1439 2879 5779 11579 23159 46327 92657 185323 370661 741337 1482707 2965421 5930887 11861791 23723597 47447201 94894427 189788857 379577741 759155483 1518310967 3036621941 6073243889 12146487779 24292975649 48585951311 97171902629 194343805267 388687610539 777375221081 1554750442183 3109500884389 6219001768781 12438003537571 24876007075181 49752014150467 99504028301131
   
   
   NB. fix the definition.  Here's the code.
   tacit_loop f.
[: }: (_1&(>:@:{`[`]})@:(, (1&p: # _1 2&p.)@:{:)@:]^:(0 ~: (>: #))^:_ x:)
   
</syntaxhighlight>
If the loop must require the output side effect, this save_if_prime definition does the trick.  Without the output hook it is probably more efficient than the copying version because it evaluates the hook <pre>(, _1 2&p.@:{:)</pre> only when isPrime is true.
<syntaxhighlight lang="j">
   extra_credit =: ([: }. ,@(',' ,.~ _3 [\ ])&.|.@:":)&>
   show =: [ ([: echo@:deb@:({. , ' ' , {:)@:extra_credit # , {:)
   save_if_prime =: (, _1 2&p.@:{:)@:show^:(isPrime@:{:)
   empty@:tacit_loop 42
1 43
2 89
3 179
4 359
5 719
6 1,439
7 2,879
8 5,779
9 11,579
10 23,159
11 46,327
12 92,657
13 185,323
14 370,661
15 741,337
16 1,482,707
17 2,965,421
18 5,930,887
19 11,861,791
20 23,723,597
21 47,447,201
22 94,894,427
23 189,788,857
24 379,577,741
25 759,155,483
26 1,518,310,967
27 3,036,621,941
28 6,073,243,889
29 12,146,487,779
30 24,292,975,649
31 48,585,951,311
32 97,171,902,629
33 194,343,805,267
34 388,687,610,539
35 777,375,221,081
36 1,554,750,442,183
37 3,109,500,884,389
38 6,219,001,768,781
39 12,438,003,537,571
40 24,876,007,075,181
41 49,752,014,150,467
42 99,504,028,301,131
</syntaxhighlight>

=={{header|Java}}==
The following uses a 'for' rather than a 'do/while' loop but otherwise is similar to the Kotlin
entry. 
<syntaxhighlight lang="java">public class LoopIncrementWithinBody {

    static final int LIMIT = 42;

    static boolean isPrime(long n) {
        if (n % 2 == 0) return n == 2;
        if (n % 3 == 0) return n == 3;
        long d = 5;
        while (d * d <= n) {
            if (n % d == 0) return false;
            d += 2;
            if (n % d == 0) return false;
            d += 4;
        }
        return true;
    }

    public static void main(String[] args) {
        long i;
        int n;
        for (i = LIMIT, n = 0; n < LIMIT; i++)
            if (isPrime(i)) {
                n++;
                System.out.printf("n = %-2d  %,19d\n", n, i);
                i += i - 1;
            }
    }
}</syntaxhighlight>

{{out}}
<pre>
Same as Kotlin entry
</pre>

=={{header|jq}}==
{{works with|jq}}
'''Works with gojq, the Go implementation of jq'''

jq's looping constructs that have a loop index do not allow that index to be modified within the loop
as such indices are "read-only", but all the looping constructs allow an index to be
be defined and modified, as illustrated by the following example, which uses "i" as the loop index.

This entry uses the jq implementation of is_prime as shown at
[[Erd%C5%91s-primes#jq]].
<syntaxhighlight lang="jq">{i:42, count:0}
| while( .count <= 42;
    .emit = null
    | .i += 1
    | if .i|is_prime 
      then
      .count += 1
      | .emit = "count at \(.i) is \(.count)"
      | .i = .i + .i - 1
      else .
      end )
| select(.emit).emit</syntaxhighlight>
{{out}}
<pre>
count at 43 is 1
count at 89 is 2
count at 179 is 3
count at 359 is 4
count at 719 is 5
count at 1439 is 6
count at 2879 is 7
count at 5779 is 8
count at 11579 is 9
count at 23159 is 10
count at 46327 is 11
count at 92657 is 12
count at 185323 is 13
count at 370661 is 14
count at 741337 is 15
count at 1482707 is 16
count at 2965421 is 17
count at 5930887 is 18
count at 11861791 is 19
count at 23723597 is 20
count at 47447201 is 21
count at 94894427 is 22
count at 189788857 is 23
count at 379577741 is 24
count at 759155483 is 25
count at 1518310967 is 26
count at 3036621941 is 27
count at 6073243889 is 28
count at 12146487779 is 29
count at 24292975649 is 30
count at 48585951311 is 31
count at 97171902629 is 32
count at 194343805267 is 33
count at 388687610539 is 34
count at 777375221081 is 35
count at 1554750442183 is 36
count at 3109500884389 is 37
count at 6219001768781 is 38
count at 12438003537571 is 39
count at 24876007075181 is 40
count at 49752014150467 is 41
count at 99504028301131 is 42
</pre>


=={{header|Julia}}==
Julia's <code>for</code> loop iterator is an iterator type which cannot be incremented as a simple variable would to change looping. 
<syntaxhighlight lang="julia">using Primes, Formatting

function doublemyindex(n=42)
    shown = 0
    i = BigInt(n)
    while shown < n
        if isprime(i + 1)
            shown += 1
            println("The index is ", format(shown, commas=true), " and ", 
                                     format(i + 1, commas=true), " is prime.")
            i += i
        end
        i += 1
    end
end

doublemyindex()
</syntaxhighlight> {{output}} <pre>
The index is 1 and 43 is prime.
The index is 2 and 89 is prime.
The index is 3 and 179 is prime.
The index is 4 and 359 is prime.
The index is 5 and 719 is prime.
The index is 6 and 1,439 is prime.
The index is 7 and 2,879 is prime.
The index is 8 and 5,779 is prime.
The index is 9 and 11,579 is prime.
The index is 10 and 23,159 is prime.
The index is 11 and 46,327 is prime.
The index is 12 and 92,657 is prime.
The index is 13 and 185,323 is prime.
The index is 14 and 370,661 is prime.
The index is 15 and 741,337 is prime.
The index is 16 and 1,482,707 is prime.
The index is 17 and 2,965,421 is prime.
The index is 18 and 5,930,887 is prime.
The index is 19 and 11,861,791 is prime.
The index is 20 and 23,723,597 is prime.
The index is 21 and 47,447,201 is prime.
The index is 22 and 94,894,427 is prime.
The index is 23 and 189,788,857 is prime.
The index is 24 and 379,577,741 is prime.
The index is 25 and 759,155,483 is prime.
The index is 26 and 1,518,310,967 is prime.
The index is 27 and 3,036,621,941 is prime.
The index is 28 and 6,073,243,889 is prime.
The index is 29 and 12,146,487,779 is prime.
The index is 30 and 24,292,975,649 is prime.
The index is 31 and 48,585,951,311 is prime.
The index is 32 and 97,171,902,629 is prime.
The index is 33 and 194,343,805,267 is prime.
The index is 34 and 388,687,610,539 is prime.
The index is 35 and 777,375,221,081 is prime.
The index is 36 and 1,554,750,442,183 is prime.
The index is 37 and 3,109,500,884,389 is prime.
The index is 38 and 6,219,001,768,781 is prime.
The index is 39 and 12,438,003,537,571 is prime.
The index is 40 and 24,876,007,075,181 is prime.
The index is 41 and 49,752,014,150,467 is prime.
The index is 42 and 99,504,028,301,131 is prime.
</pre>

=={{header|Kotlin}}==
Unlike many other C-family languages (notably Java), Kotlin's 'for' statement doesn't allow either the iteration variable or the step to be modified within the loop body. 

So instead we use a do/while loop here which has no such restrictions.
<syntaxhighlight lang="scala">// version 1.2.60

fun isPrime(n: Long): Boolean {
    if (n % 2L == 0L) return n == 2L
    if (n % 3L == 0L) return n == 3L
    var d = 5L
    while (d * d <= n) {
        if (n % d == 0L) return false
        d += 2L
        if (n % d == 0L) return false
        d += 4L
    }
    return true
}

fun main(args: Array<String>) {
    var i = 42L
    var n = 0
    do {
        if (isPrime(i)) {
            n++
            System.out.printf("n = %-2d  %,19d\n", n, i)
            i += i - 1
        }
        i++
    }
    while (n < 42)
}</syntaxhighlight>
{{out}}
<pre style="height:35ex">n = 1                    43
n = 2                    89
n = 3                   179
n = 4                   359
n = 5                   719
n = 6                 1,439
n = 7                 2,879
n = 8                 5,779
n = 9                11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131</pre>

Although Kotlin is predominantly an object-oriented/procedural language, it does have some features which enable one to program in a functional style. These features include 'tail recursion' which, of course, is commonly used in place of loops in purely functional languages. 

In such cases, the Kotlin compiler optimizes out the recursion, leaving behind a fast and efficient loop based version instead.

The following version uses a tail recursive function rather than a while loop to achieve the same effect:

<syntaxhighlight lang="scala">// version 1.2.60

fun isPrime(n: Long): Boolean {
    if (n % 2L == 0L) return n == 2L
    if (n % 3L == 0L) return n == 3L
    var d = 5L
    while (d * d <= n) {
        if (n % d == 0L) return false
        d += 2L
        if (n % d == 0L) return false
        d += 4L
    }
    return true
}

tailrec fun loop(index: Long, numPrimes: Int) {
    if (numPrimes == 42) return
    var i = index
    var n = numPrimes 
    if (isPrime(i)) {
        n++
        System.out.printf("n = %-2d  %,19d\n", n, i)
        loop(2 * i - 1, n)
    }
    else loop(++i, n)
}

fun main(args: Array<String>) {    
    loop(42, 0)
}</syntaxhighlight>    

{{out}}
<pre>
Same as 'while' loop version.
</pre>

=={{header|Ksh}}==
<syntaxhighlight lang="ksh">
#!/bin/ksh

# Increment loop index within loop body

#	# Variables:
#
integer INDX_START=42 N_PRIMES=42

#	# Functions:
#

#	# Function _isprime(n) return 1 for prime, 0 for not prime
#
function _isprime {
	typeset _n ; integer _n=$1
	typeset _i ; integer _i

	(( _n < 2 )) && return 0
	for (( _i=2 ; _i*_i<=_n ; _i++ )); do
		(( ! ( _n % _i ) )) && return 0
	done
	return 1
}

 ######
# main #
 ######
integer i n=0
for ((i=INDX_START; n<N_PRIMES; i++)); do
	_isprime ${i}
	if (( $? )); then
		printf "%,18d is prime, %2d primes found(so far)\n" ${i} $((++n))
		(( i+=$i ))
	fi
done</syntaxhighlight>
{{out}}<pre>
                43 is prime,  1 primes found(so far)
                89 is prime,  2 primes found(so far)
               179 is prime,  3 primes found(so far)
               359 is prime,  4 primes found(so far)
               719 is prime,  5 primes found(so far)
             1,439 is prime,  6 primes found(so far)
             2,879 is prime,  7 primes found(so far)
             5,779 is prime,  8 primes found(so far)
            11,579 is prime,  9 primes found(so far)
            23,159 is prime, 10 primes found(so far)
            46,327 is prime, 11 primes found(so far)
            92,657 is prime, 12 primes found(so far)
           185,323 is prime, 13 primes found(so far)
           370,661 is prime, 14 primes found(so far)
           741,337 is prime, 15 primes found(so far)
         1,482,707 is prime, 16 primes found(so far)
         2,965,421 is prime, 17 primes found(so far)
         5,930,887 is prime, 18 primes found(so far)
        11,861,791 is prime, 19 primes found(so far)
        23,723,597 is prime, 20 primes found(so far)
        47,447,201 is prime, 21 primes found(so far)
        94,894,427 is prime, 22 primes found(so far)
       189,788,857 is prime, 23 primes found(so far)
       379,577,741 is prime, 24 primes found(so far)
       759,155,483 is prime, 25 primes found(so far)
     1,518,310,967 is prime, 26 primes found(so far)
     3,036,621,941 is prime, 27 primes found(so far)
     6,073,243,889 is prime, 28 primes found(so far)
    12,146,487,779 is prime, 29 primes found(so far)
    24,292,975,649 is prime, 30 primes found(so far)
    48,585,951,311 is prime, 31 primes found(so far)
    97,171,902,629 is prime, 32 primes found(so far)
   194,343,805,267 is prime, 33 primes found(so far)
   388,687,610,539 is prime, 34 primes found(so far)
   777,375,221,081 is prime, 35 primes found(so far)
 1,554,750,442,183 is prime, 36 primes found(so far)
 3,109,500,884,389 is prime, 37 primes found(so far)
 6,219,001,768,781 is prime, 38 primes found(so far)
12,438,003,537,571 is prime, 39 primes found(so far)
24,876,007,075,181 is prime, 40 primes found(so far)
49,752,014,150,467 is prime, 41 primes found(so far)
99,504,028,301,131 is prime, 42 primes found(so far)</pre>

=={{header|Lambdatalk}}==
We use the javascript bigInts and the isPrime primitive working on big integers.

<syntaxhighlight lang="scheme">

{isPrime 11} 
-> true

{isPrime 99504028301131}
-> true 

{def upto
 {def upto.loop
 {lambda {:max :i :n}
  {if {> :n :max}
   then 
   else {if {isPrime :i}
         then {tr {td n = :n} {td {@ style="text-align:right"} :i}}
              {upto.loop :max
                         {BI.+ :i {BI.- :i 1}} 
                         {BI.+ :n 1}}
         else {upto.loop :max
                         {BI.+ :i 1}
                         :n} }}}}
 {lambda {:n}
  {upto.loop :n 42 1} }}   
-> upto 

{table
 {upto 42}
}
-> 
n = 1	            43
n = 2	            89
n = 3	           179
n = 4	           359
n = 5	           719
n = 6	          1439
n = 7	          2879
n = 8	          5779
n = 9	         11579
n = 10	         23159
n = 11	         46327
n = 12	         92657
n = 13	        185323
n = 14	        370661
n = 15	        741337
n = 16	       1482707
n = 17	       2965421
n = 18	       5930887
n = 19	      11861791
n = 20	      23723597
n = 21	      47447201
n = 22	      94894427
n = 23	     189788857
n = 24	     379577741
n = 25	     759155483
n = 26	    1518310967
n = 27	    3036621941
n = 28	    6073243889
n = 29	   12146487779
n = 30	   24292975649
n = 31	   48585951311
n = 32	   97171902629
n = 33	  194343805267
n = 34	  388687610539
n = 35	  777375221081
n = 36	 1554750442183
n = 37	 3109500884389
n = 38	 6219001768781
n = 39	12438003537571
n = 40	24876007075181
n = 41 	49752014150467
n = 42 	99504028301131
</syntaxhighlight>

=={{header|Lua}}==
<syntaxhighlight lang="lua">-- Returns boolean indicate whether x is prime
function isPrime (x)
  if x < 2 then return false end
  if x < 4 then return true end
  if x % 2 == 0 then return false end
  for d = 3, math.sqrt(x), 2 do
    if x % d == 0 then return false end
  end
  return true
end

-- Main procedure
local n, i = 0, 42
while n < 42 do
  if isPrime(i) then
    n = n + 1
    print("n = " .. n, i)
    i = 2 * i - 1
  end
  i = i + 1
end</syntaxhighlight>
{{out}}
<pre>n = 1   43
n = 2   89
n = 3   179
n = 4   359
n = 5   719
n = 6   1439
n = 7   2879
n = 8   5779
n = 9   11579
n = 10  23159
n = 11  46327
n = 12  92657
n = 13  185323
n = 14  370661
n = 15  741337
n = 16  1482707
n = 17  2965421
n = 18  5930887
n = 19  11861791
n = 20  23723597
n = 21  47447201
n = 22  94894427
n = 23  189788857
n = 24  379577741
n = 25  759155483
n = 26  1518310967
n = 27  3036621941
n = 28  6073243889
n = 29  12146487779
n = 30  24292975649
n = 31  48585951311
n = 32  97171902629
n = 33  194343805267
n = 34  388687610539
n = 35  777375221081
n = 36  1554750442183
n = 37  3109500884389
n = 38  6219001768781
n = 39  12438003537571
n = 40  24876007075181
n = 41  49752014150467
n = 42  99504028301131</pre>

=={{header|M2000 Interpreter}}==
<syntaxhighlight lang="m2000 interpreter">
Module CheckIt {
      Function IsPrime (x) {
            if x<=5 OR frac(x) then {
                  if x = 2 OR x = 3 OR x = 5 then =true
                  Break
            }
            if x mod 2 else exit
            if x mod 3 else exit
            x1=sqrt(x): d=5@
            {if x mod d else exit
                  d += 2@: if d>x1 then =true : exit
                  if x mod d else exit
                  d += 4@: if d<= x1 else =true: exit
                  loop
             }
      }
      \\ For Next loops or For {} loops can't change iterator variable (variable has a copy of real iterator)
      \\ In those loops we have to use Continue to skip lines and repeat the loop.
      \\ so we have to use Block iterator, using Loop which set a flag current block to repeat itself once.
      def long Limit=42, n
      def decimal i
      i=Limit
      {
            if n<Limit Else exit
            if isPrime(i)  then n++ : Print format$("n={0::2}: {1:-20}", n, str$(i,"#,###")) : i+=i-1
            i++
            loop 
      }
}
CheckIt
</syntaxhighlight>

{{out}}
<pre>
Same as Kotlin entry
</pre>

=={{header|Maple}}==
A translation of Kotlin entry
<syntaxhighlight lang="maple">i := 42:
count := 0:
while(count < 42) do
	i := i+1:
	if type(i,prime) then
		count := count + 1:
		printf("n=%-2d     %19d\n", count,i):
		i := 2*i -1:
	end if:
end do:</syntaxhighlight>
{{Out|Output}}
<pre>n=1                       43
n=2                       89
n=3                      179
n=4                      359
n=5                      719
n=6                     1439
n=7                     2879
n=8                     5779
n=9                    11579
n=10                   23159
n=11                   46327
n=12                   92657
n=13                  185323
n=14                  370661
n=15                  741337
n=16                 1482707
n=17                 2965421
n=18                 5930887
n=19                11861791
n=20                23723597
n=21                47447201
n=22                94894427
n=23               189788857
n=24               379577741
n=25               759155483
n=26              1518310967
n=27              3036621941
n=28              6073243889
n=29             12146487779
n=30             24292975649
n=31             48585951311
n=32             97171902629
n=33            194343805267
n=34            388687610539
n=35            777375221081
n=36           1554750442183
n=37           3109500884389
n=38           6219001768781
n=39          12438003537571
n=40          24876007075181
n=41          49752014150467
n=42          99504028301131</pre>

=={{header|Mathematica}} / {{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">{i, n} = {42, 0};
While[n < 42,
 If[PrimeQ[i],
  Print["n=", n++, "\t", i];
  i += i - 1;
  ];
 i++;
 ]</syntaxhighlight>
{{out}}
<pre>n=0	43
n=1	89
n=2	179
n=3	359
n=4	719
n=5	1439
n=6	2879
n=7	5779
n=8	11579
n=9	23159
n=10	46327
n=11	92657
n=12	185323
n=13	370661
n=14	741337
n=15	1482707
n=16	2965421
n=17	5930887
n=18	11861791
n=19	23723597
n=20	47447201
n=21	94894427
n=22	189788857
n=23	379577741
n=24	759155483
n=25	1518310967
n=26	3036621941
n=27	6073243889
n=28	12146487779
n=29	24292975649
n=30	48585951311
n=31	97171902629
n=32	194343805267
n=33	388687610539
n=34	777375221081
n=35	1554750442183
n=36	3109500884389
n=37	6219001768781
n=38	12438003537571
n=39	24876007075181
n=40	49752014150467
n=41	99504028301131</pre>

=={{header|Microsoft Small Basic}}==
Small Basic allows to modify the index inside the loop.
<syntaxhighlight lang="smallbasic">'Loops Increment loop index within loop body - 16/07/2018
imax=42
i=0
n=42
While i<imax
  isprime_n()
  If ret_isprime_n Then
    i=i+1
    format_i()
    format_n()
    TextWindow.WriteLine("i="+ret_format_i+" : "+ret_format_n)
    n=n+n-1
  EndIf
  n=n+1
EndWhile

Sub isprime_n 
  If n=2 Or n=3 Then
    ret_isprime_n="True"
  ElseIf Math.Remainder(n,2)=0 Or Math.Remainder(n,3)=0 Then 
    ret_isprime_n="False"
  Else
    j=5
    While j*j<=n
      If Math.Remainder(n,j)=0 Or Math.Remainder(n,j+2)=0 Then 
        ret_isprime_n="False"
        Goto exitsub
      EndIf
      j=j+6
    EndWhile
    ret_isprime_n="True"
  EndIf
exitsub:
EndSub 'isprime_n

Sub format_i
  ret_format_i=Text.GetSubText("   ",1,3-Text.GetLength(i))+i
EndSub 'format_i

Sub format_n
  nn="" 
  l=-1
  For k=Text.GetLength(n) To 1 Step -1
    l=l+1
    cc=Text.GetSubText(n,k,1)
    If l=3 Then
      cv=","
      l=0
    Else
      cv=""
    EndIf
    nn=Text.Append(cc,Text.Append(cv,nn))
  EndFor
  space="                    "
  nn=Text.GetSubText(space,1,Text.GetLength(space)-Text.GetLength(nn))+nn
  ret_format_n=nn
EndSub 'format_n</syntaxhighlight>
{{out}}
<pre style="height:60ex">
i= 1 :                   43
i= 2 :                   89
i= 3 :                  179
i= 4 :                  359
i= 5 :                  719
i= 6 :                1,439
i= 7 :                2,879
i= 8 :                5,779
i= 9 :               11,579
i=10 :               23,159
i=11 :               46,327
i=12 :               92,657
i=13 :              185,323
i=14 :              370,661
i=15 :              741,337
i=16 :            1,482,707
i=17 :            2,965,421
i=18 :            5,930,887
i=19 :           11,861,791
i=20 :           23,723,597
i=21 :           47,447,201
i=22 :           94,894,427
i=23 :          189,788,857
i=24 :          379,577,741
i=25 :          759,155,483
i=26 :        1,518,310,967
i=27 :        3,036,621,941
i=28 :        6,073,243,889
i=29 :       12,146,487,779
i=30 :       24,292,975,649
i=31 :       48,585,951,311
i=32 :       97,171,902,629
i=33 :      194,343,805,267
i=34 :      388,687,610,539
i=35 :      777,375,221,081
i=36 :    1,554,750,442,183
i=37 :    3,109,500,884,389
i=38 :    6,219,001,768,781
i=39 :   12,438,003,537,571
i=40 :   24,876,007,075,181
i=41 :   49,752,014,150,467
i=42 :   99,504,028,301,131
</pre>

=={{header|Nanoquery}}==
{{trans|Java}}
<syntaxhighlight lang="nanoquery">limit = 42

def isPrime(n)
    if ((n % 2) = 0) or ((n % 3) = 0)
        return false
    end
    d = 5
    while (d * d) <= n
        if (n % d) = 0
            return false
        end
        d += 2
        if (n % d) = 0
            return false
        end
        d += 4
    end
    return true
end

i = limit
for (n = 0) (n < limit) (i += 1)
    if isPrime(i)
        n += 1
        print format("n = %-2d  %,19d\n", n, i)
        i += i - 1
    end
end</syntaxhighlight>

{{out}}
<pre>n = 1                    43
n = 2                    89
n = 3                   179
n = 4                   359
n = 5                   719
n = 6                 1,439
n = 7                 2,879
n = 8                 5,779
n = 9                11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131</pre>

=={{header|NewLISP}}==
<syntaxhighlight lang="newlisp">
#! /usr/local/bin/newlisp

(define (prime? n)
 (and 
   (set 'lst (factor n))
   (= (length lst) 1)))

(define (thousands_separator i)
    (setq i (string i))
    (setq len (length i))
    (setq i (reverse (explode i)))
    (setq o "")
    (setq count3 0)
    (dolist (x i)
        (setq o (string o x))
        (inc count3)
        (if (and (= 3 count3) (< (+ $idx 1) len))
            (begin
            (setq o (string o "_"))
            (setq count3 0))))
            
    (reverse o))


;- - - Main begins here
(setq i 42)
(setq n 0)
(while (< n 42)
    (if (prime? i)
        (begin
            (inc n)
            (println (string "n = " n " -> " (thousands_separator i)))
            (setq i (+ i i -1))))
    (inc i)        
)

(exit)
</syntaxhighlight>

<pre>
n = 1 -> 43
n = 2 -> 89
n = 3 -> 179
n = 4 -> 359
n = 5 -> 719
n = 6 -> 1_439
n = 7 -> 2_879
n = 8 -> 5_779
n = 9 -> 11_579
n = 10 -> 23_159
n = 11 -> 46_327
n = 12 -> 92_657
n = 13 -> 185_323
n = 14 -> 370_661
n = 15 -> 741_337
n = 16 -> 1_482_707
n = 17 -> 2_965_421
n = 18 -> 5_930_887
n = 19 -> 11_861_791
n = 20 -> 23_723_597
n = 21 -> 47_447_201
n = 22 -> 94_894_427
n = 23 -> 189_788_857
n = 24 -> 379_577_741
n = 25 -> 759_155_483
n = 26 -> 1_518_310_967
n = 27 -> 3_036_621_941
n = 28 -> 6_073_243_889
n = 29 -> 12_146_487_779
n = 30 -> 24_292_975_649
n = 31 -> 48_585_951_311
n = 32 -> 97_171_902_629
n = 33 -> 194_343_805_267
n = 34 -> 388_687_610_539
n = 35 -> 777_375_221_081
n = 36 -> 1_554_750_442_183
n = 37 -> 3_109_500_884_389
n = 38 -> 6_219_001_768_781
n = 39 -> 12_438_003_537_571
n = 40 -> 24_876_007_075_181
n = 41 -> 49_752_014_150_467
n = 42 -> 99_504_028_301_131

</pre>

=={{header|Nim}}==
In Nim, loop index is read-only, so we have to use a normal variable and increment it as needed.
<syntaxhighlight lang="nim">
import strformat
from strutils import insertSep

func isPrime(i: int): bool =
  if i == 2 or i == 3: return true
  elif i mod 2 == 0 or i mod 3 == 0: return false
  var idx = 5
  while idx*idx <= i:
    if i mod idx == 0: return false
    idx.inc 2
    if i mod idx == 0: return false
    idx.inc 4
  result = true

const limit = 42
proc main =
  var
    i = 42
    n = 0
  while n < limit:
    if i.isPrime:
      inc n
      echo &"""n {n:>2} = {($i).insertSep(sep=','):>19}"""
      i.inc i
      continue
    inc i

main()
</syntaxhighlight>
{{out}}
<pre style="height:50ex">
n  1 =                  43
n  2 =                  89
n  3 =                 179
n  4 =                 359
n  5 =                 719
n  6 =               1,439
n  7 =               2,879
n  8 =               5,779
n  9 =              11,579
n 10 =              23,159
n 11 =              46,327
n 12 =              92,657
n 13 =             185,323
n 14 =             370,661
n 15 =             741,337
n 16 =           1,482,707
n 17 =           2,965,421
n 18 =           5,930,887
n 19 =          11,861,791
n 20 =          23,723,597
n 21 =          47,447,201
n 22 =          94,894,427
n 23 =         189,788,857
n 24 =         379,577,741
n 25 =         759,155,483
n 26 =       1,518,310,967
n 27 =       3,036,621,941
n 28 =       6,073,243,889
n 29 =      12,146,487,779
n 30 =      24,292,975,649
n 31 =      48,585,951,311
n 32 =      97,171,902,629
n 33 =     194,343,805,267
n 34 =     388,687,610,539
n 35 =     777,375,221,081
n 36 =   1,554,750,442,183
n 37 =   3,109,500,884,389
n 38 =   6,219,001,768,781
n 39 =  12,438,003,537,571
n 40 =  24,876,007,075,181
n 41 =  49,752,014,150,467
n 42 =  99,504,028,301,131
</pre>

=={{header|Perl}}==
Messing with the loop iterator value doesn't go well in Perl, so use the <tt>while</tt> loop alternative. The <code>ntheory</code> module is used to test for primes.
{{trans|Kotlin}}
{{libheader|ntheory}}
<syntaxhighlight lang="perl">use ntheory qw(is_prime);

$i = 42;
while ($n < 42) {
    if (is_prime($i)) {
        $n++;
        printf "%2d %21s\n", $n, commatize($i);
        $i += $i - 1;
    }
    $i++;
}

sub commatize {
    (my $s = reverse shift) =~ s/(.{3})/$1,/g;
    $s =~ s/,$//;
    $s = reverse $s;
}</syntaxhighlight>
{{out}}
<pre  style="height:30ex"> 1                    43
 2                    89
 3                   179
 4                   359
 5                   719
 6                 1,439
 7                 2,879
 8                 5,779
 9                11,579
10                23,159
11                46,327
12                92,657
13               185,323
14               370,661
15               741,337
16             1,482,707
17             2,965,421
18             5,930,887
19            11,861,791
20            23,723,597
21            47,447,201
22            94,894,427
23           189,788,857
24           379,577,741
25           759,155,483
26         1,518,310,967
27         3,036,621,941
28         6,073,243,889
29        12,146,487,779
30        24,292,975,649
31        48,585,951,311
32        97,171,902,629
33       194,343,805,267
34       388,687,610,539
35       777,375,221,081
36     1,554,750,442,183
37     3,109,500,884,389
38     6,219,001,768,781
39    12,438,003,537,571
40    24,876,007,075,181
41    49,752,014,150,467
42    99,504,028,301,131</pre>

=={{header|Phix}}==
Phix does not allow for loop variables to be modified, so we must use a while loop and manual increment for this sort of thing.
<!--<syntaxhighlight lang="phix">-->
 <span style="color: #004080;">atom</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">42</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span>
 <span style="color: #008080;">while</span> <span style="color: #000000;">n</span><span style="color: #0000FF;"><=</span><span style="color: #000000;">42</span> <span style="color: #008080;">do</span>
     <span style="color: #008080;">if</span> <span style="color: #7060A8;">is_prime</span><span style="color: #0000FF;">(</span><span style="color: #000000;">i</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">then</span>
         <span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"n = %-2d  %,19d\n"</span><span style="color: #0000FF;">,</span> <span style="color: #0000FF;">{</span><span style="color: #000000;">n</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">})</span>
         <span style="color: #000000;">n</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
         <span style="color: #000000;">i</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span>
     <span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
     <span style="color: #000000;">i</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
 <span style="color: #008080;">end</span> <span style="color: #008080;">while</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
n = 1                    43
n = 2                    89
n = 3                   179
n = 4                   359
n = 5                   719
n = 6                 1,439
n = 7                 2,879
n = 8                 5,779
n = 9                11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131
</pre>

=={{header|Python}}==
===Procedural===
<syntaxhighlight lang="python">def isPrime(n):
    for x in 2, 3:
        if not n % x:
            return n == x
    d = 5
    while d * d <= n:
        for x in 2, 4:
            if not n % d:
                return False
            d += x
    return True

i = 42
n = 0
while n < 42:
    if isPrime(i):
        n += 1
        print('n = {:2} {:20,}'.format(n, i))
        i += i - 1
    i += 1</syntaxhighlight>
{{out}}
<pre>n =  1                   43
n =  2                   89
n =  3                  179
n =  4                  359
n =  5                  719
n =  6                1,439
n =  7                2,879
n =  8                5,779
n =  9               11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131</pre>

===Functional===

This task is defined in terms of procedural 'loops', which can generally be understood in functional terms as implementations of folds or maps. An analogous functional construction here might be a non-finite generator, or the iterative application of a function (over a tuple of values) to a seed value, for example:

<syntaxhighlight lang="python">'''Loops/Increment loop index within loop body.'''

from itertools import islice, takewhile
from functools import reduce
import operator


# main :: IO ()
def main():
    '''Defines a list value, while printing a stream
       of intermediate values during computation.
    '''
    gt = curry(operator.gt)
    fst = operator.itemgetter(0)

    list(takewhile(compose(gt(43), fst), series()))


# series :: (Int, Int) -> [(Int, Int)]
def series():
    '''Non finite series, defined as a generator
       with IO side-effects (to the print channel).
    '''
    def go(tpl):
        if isPrime(tpl[1]):
            # Side effect.
            print(showTuple(tpl))
            # Value.
            return splitArrow(succ)(dbl)(tpl)
        else:
            return secondArrow(succ)(tpl)

    return iterate(go)(
        (1, 42)
    )


# isPrime :: Int -> Bool
def isPrime(n):
    '''True if n is prime.'''
    if n in (2, 3):
        return True
    if 2 > n or 0 == n % 2:
        return False
    if 9 > n:
        return True
    if 0 == n % 3:
        return False

    def p(x):
        return 0 == n % x or 0 == n % (2 + x)

    return not any(map(p, range(5, 1 + int(n ** 0.5), 6)))


# showTuple :: (Int, Int) -> String
def showTuple(tpl):
    '''Second integer shown with comma-chunked digits.'''
    return '{:2} -> {:20,}'.format(*tpl)


# -------------------------GENERIC-------------------------

# compose :: ((a -> a), ...) -> (a -> a)
def compose(*fs):
    '''Composition, from right to left,
       of a series of functions.
    '''
    return lambda x: reduce(
        lambda a, f: f(a),
        fs[::-1], x
    )


# curry :: ((a, b) -> c) -> a -> b -> c
def curry(f):
    '''A curried function derived
       from an uncurried function.
    '''
    return lambda x: lambda y: f(x, y)


# dbl :: Int -> Int -> Int
def dbl(x):
    '''2 * x'''
    return x + x


# drop :: Int -> [a] -> [a]
# drop :: Int -> String -> String
def drop(n):
    '''The sublist of xs beginning at
       (zero-based) index n.
    '''
    def go(xs):
        take(n)(xs)
        return xs
    return go


# iterate :: (a -> a) -> a -> Gen [a]
def iterate(f):
    '''An infinite list of repeated
       applications of f to x.
    '''
    def go(x):
        v = x
        while True:
            yield v
            v = f(v)
    return go


# secondArrow :: (b -> c) -> (a, b...) -> (a, c ...)
def secondArrow(f):
    '''A simple function lifted to one which applies
       to a tuple, transforming only its second value.
    '''
    return lambda tpl: (tpl[0], f(tpl[1]))


# splitArrow (***) :: (a -> b) -> (c -> d) -> ((a, c) -> (b, d))
def splitArrow(f):
    '''A function from (x, y) to a tuple of (f(x), g(y))
    '''
    return lambda g: lambda tpl: (f(tpl[0]), g(tpl[1]))


# succ :: Enum a => a -> a
def succ(x):
    '''The successor of a value.
       For numeric types, (1 +).
    '''
    return 1 + x


# take :: Int -> [a] -> [a]
# take :: Int -> String -> String
def take(n):
    '''The prefix of xs of length n,
       or xs itself if n > length xs.
    '''
    return lambda xs: list(islice(xs, n))


# MAIN ---
if __name__ == '__main__':
    main()</syntaxhighlight>
{{Out}}
<pre> 1 ->                   43
 2 ->                   89
 3 ->                  179
 4 ->                  359
 5 ->                  719
 6 ->                1,439
 7 ->                2,879
 8 ->                5,779
 9 ->               11,579
10 ->               23,159
11 ->               46,327
12 ->               92,657
13 ->              185,323
14 ->              370,661
15 ->              741,337
16 ->            1,482,707
17 ->            2,965,421
18 ->            5,930,887
19 ->           11,861,791
20 ->           23,723,597
21 ->           47,447,201
22 ->           94,894,427
23 ->          189,788,857
24 ->          379,577,741
25 ->          759,155,483
26 ->        1,518,310,967
27 ->        3,036,621,941
28 ->        6,073,243,889
29 ->       12,146,487,779
30 ->       24,292,975,649
31 ->       48,585,951,311
32 ->       97,171,902,629
33 ->      194,343,805,267
34 ->      388,687,610,539
35 ->      777,375,221,081
36 ->    1,554,750,442,183
37 ->    3,109,500,884,389
38 ->    6,219,001,768,781
39 ->   12,438,003,537,571
40 ->   24,876,007,075,181
41 ->   49,752,014,150,467
42 ->   99,504,028,301,131</pre>
=={{header|R}}==
R cannot complete this task with a for loop. See https://stackoverflow.com/a/5913329/ . Instead, we must go down the same path as the Kotlin solution. Because it is sufficient for numbers this small, we will save ourselves some work and use the gmp library's isprime function for checking if a number is prime.
<syntaxhighlight lang="rsplus">i <- 42
primeCount <- 0
while(primeCount < 42)
{
  if(gmp::isprime(i) == 2)#1 means "probably prime" and won't come up for numbers this small, 2 is what we want.
  {
    primeCount <- primeCount + 1
    extraCredit <- format(i, big.mark=",", scientific = FALSE)
    cat("Prime count:", paste0(primeCount, ";"), "The prime just found was:", extraCredit, "\n")
    i <- i + i#This is missing the -1 from the Kotlin solution. There is no need to check i + i (it's even).
  }
  i <- i + 1
}</syntaxhighlight>
{{Out}}
<pre>Prime count: 1; The prime just found was: 43 
Prime count: 2; The prime just found was: 89 
Prime count: 3; The prime just found was: 179 
Prime count: 4; The prime just found was: 359 
Prime count: 5; The prime just found was: 719 
Prime count: 6; The prime just found was: 1,439 
Prime count: 7; The prime just found was: 2,879 
Prime count: 8; The prime just found was: 5,779 
Prime count: 9; The prime just found was: 11,579 
Prime count: 10; The prime just found was: 23,159 
Prime count: 11; The prime just found was: 46,327 
Prime count: 12; The prime just found was: 92,657 
Prime count: 13; The prime just found was: 185,323 
Prime count: 14; The prime just found was: 370,661 
Prime count: 15; The prime just found was: 741,337 
Prime count: 16; The prime just found was: 1,482,707 
Prime count: 17; The prime just found was: 2,965,421 
Prime count: 18; The prime just found was: 5,930,887 
Prime count: 19; The prime just found was: 11,861,791 
Prime count: 20; The prime just found was: 23,723,597 
Prime count: 21; The prime just found was: 47,447,201 
Prime count: 22; The prime just found was: 94,894,427 
Prime count: 23; The prime just found was: 189,788,857 
Prime count: 24; The prime just found was: 379,577,741 
Prime count: 25; The prime just found was: 759,155,483 
Prime count: 26; The prime just found was: 1,518,310,967 
Prime count: 27; The prime just found was: 3,036,621,941 
Prime count: 28; The prime just found was: 6,073,243,889 
Prime count: 29; The prime just found was: 12,146,487,779 
Prime count: 30; The prime just found was: 24,292,975,649 
Prime count: 31; The prime just found was: 48,585,951,311 
Prime count: 32; The prime just found was: 97,171,902,629 
Prime count: 33; The prime just found was: 194,343,805,267 
Prime count: 34; The prime just found was: 388,687,610,539 
Prime count: 35; The prime just found was: 777,375,221,081 
Prime count: 36; The prime just found was: 1,554,750,442,183 
Prime count: 37; The prime just found was: 3,109,500,884,389 
Prime count: 38; The prime just found was: 6,219,001,768,781 
Prime count: 39; The prime just found was: 12,438,003,537,571 
Prime count: 40; The prime just found was: 24,876,007,075,181 
Prime count: 41; The prime just found was: 49,752,014,150,467 
Prime count: 42; The prime just found was: 99,504,028,301,131</pre>

=={{header|Racket}}==

Racket's <code>for</code> doesn't allow modification of index on the fly. The usual idiom for writing this kind of loop is to use named let, as shown here.

<syntaxhighlight lang="racket">#lang racket

(require math/number-theory)

(define (comma x)
  (string-join
   (reverse
    (for/list ([digit (in-list (reverse (string->list (~a x))))] [i (in-naturals)])
      (cond
        [(and (= 0 (modulo i 3)) (> i 0)) (string digit #\,)]
        [else (string digit)])))
   ""))

(let loop ([x 42] [cnt 0])
  (cond
    [(= cnt 42) (void)]
    [(prime? x) (printf "~a: ~a\n" (add1 cnt) (comma x))
                (loop (* 2 x) (add1 cnt))]
    [else (loop (add1 x) cnt)]))</syntaxhighlight>

{{out}}
<pre>
1: 43
2: 89
3: 179
4: 359
5: 719
6: 1,439
7: 2,879
8: 5,779
9: 11,579
10: 23,159
11: 46,327
12: 92,657
13: 185,323
14: 370,661
15: 741,337
16: 1,482,707
17: 2,965,421
18: 5,930,887
19: 11,861,791
20: 23,723,597
21: 47,447,201
22: 94,894,427
23: 189,788,857
24: 379,577,741
25: 759,155,483
26: 1,518,310,967
27: 3,036,621,941
28: 6,073,243,889
29: 12,146,487,779
30: 24,292,975,649
31: 48,585,951,311
32: 97,171,902,629
33: 194,343,805,267
34: 388,687,610,539
35: 777,375,221,081
36: 1,554,750,442,183
37: 3,109,500,884,389
38: 6,219,001,768,781
39: 12,438,003,537,571
40: 24,876,007,075,181
41: 49,752,014,150,467
42: 99,504,028,301,131
</pre>

=={{header|Raku}}==
(formerly Perl 6)
Hmm.
<blockquote>Demonstrate the best way to accomplish this. </blockquote>
The ''best'' way is probably to not use an explicit loop. Just calculate the sequence directly.

<syntaxhighlight lang="raku" line># the actual sequence logic
my @seq = grep *.is-prime, (42, { .is-prime ?? $_+<1 !! $_+1 } … *);

# display code
say (1+$_).fmt("%-4s"), @seq[$_].flip.comb(3).join(',').flip.fmt("%20s") for ^42;</syntaxhighlight>
{{out}}
<pre>1                     43
2                     89
3                    179
4                    359
5                    719
6                  1,439
7                  2,879
8                  5,779
9                 11,579
10                23,159
11                46,327
12                92,657
13               185,323
14               370,661
15               741,337
16             1,482,707
17             2,965,421
18             5,930,887
19            11,861,791
20            23,723,597
21            47,447,201
22            94,894,427
23           189,788,857
24           379,577,741
25           759,155,483
26         1,518,310,967
27         3,036,621,941
28         6,073,243,889
29        12,146,487,779
30        24,292,975,649
31        48,585,951,311
32        97,171,902,629
33       194,343,805,267
34       388,687,610,539
35       777,375,221,081
36     1,554,750,442,183
37     3,109,500,884,389
38     6,219,001,768,781
39    12,438,003,537,571
40    24,876,007,075,181
41    49,752,014,150,467
42    99,504,028,301,131</pre>

=={{header|REXX}}==
<syntaxhighlight lang="rexx">/*REXX pgm displays primes found:  starting Z at 42, if Z is a prime, add Z, else add 1.*/
numeric digits 20;              d=digits()       /*ensure enough decimal digits for  Z. */
parse arg limit .                                /*obtain optional arguments from the CL*/
if limit=='' | limit==","  then limit=42         /*Not specified?  Then use the default.*/
n=0                                              /*the count of number of primes found. */
     do z=42  until n==limit                     /* ◄──this DO loop's index is modified.*/
     if isPrime(z)  then do;  n=n + 1            /*Z  a prime?  Them bump prime counter.*/
                              say right('n='n, 9)     right(commas(z), d)
                              z=z + z - 1        /*also, bump the  DO  loop index  Z.   */
                         end
     end   /*z*/                                 /* [↑] a small tribute to Douglas Adams*/
exit                                             /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
commas:  parse arg _;  do j=length(_)-3  to 1  by -3; _=insert(',', _, j); end;   return _
/*──────────────────────────────────────────────────────────────────────────────────────*/
isPrime: procedure; parse arg #;         if wordpos(#, '2 3 5 7')\==0  then return 1
                                         if # // 2==0 | # // 3    ==0  then return 0
           do j=5  by 6  until j*j>#;    if # // j==0 | # // (J+2)==0  then return 0
           end   /*j*/                           /*           ___                       */
         return 1                                /*Exceeded  √ #  ?    Then # is prime. */</syntaxhighlight>
{{out|output}}
<pre>
      n=1                   43
      n=2                   89
      n=3                  179
      n=4                  359
      n=5                  719
      n=6                1,439
      n=7                2,879
      n=8                5,779
      n=9               11,579
     n=10               23,159
     n=11               46,327
     n=12               92,657
     n=13              185,323
     n=14              370,661
     n=15              741,337
     n=16            1,482,707
     n=17            2,965,421
     n=18            5,930,887
     n=19           11,861,791
     n=20           23,723,597
     n=21           47,447,201
     n=22           94,894,427
     n=23          189,788,857
     n=24          379,577,741
     n=25          759,155,483
     n=26        1,518,310,967
     n=27        3,036,621,941
     n=28        6,073,243,889
     n=29       12,146,487,779
     n=30       24,292,975,649
     n=31       48,585,951,311
     n=32       97,171,902,629
     n=33      194,343,805,267
     n=34      388,687,610,539
     n=35      777,375,221,081
     n=36    1,554,750,442,183
     n=37    3,109,500,884,389
     n=38    6,219,001,768,781
     n=39   12,438,003,537,571
     n=40   24,876,007,075,181
     n=41   49,752,014,150,467
     n=42   99,504,028,301,131
</pre>

=={{header|Ring}}==
<syntaxhighlight lang="ring">
# Project : Loops/Increment loop index within loop body

load "stdlib.ring"
i = 42
n = 0
while n < 42
         if isprime(i) 
            n = n + 1
            see "n = " + n + "    " + i + nl
            i = i + i - 1
         ok
         i = i + 1
end
</syntaxhighlight>
Output:
<pre>
n = 1                    43
n = 2                    89
n = 3                   179
n = 4                   359
n = 5                   719
n = 6                 1,439
n = 7                 2,879
n = 8                 5,779
n = 9                11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131</pre>

=={{header|Ruby}}==
<syntaxhighlight lang="ruby">
require 'prime'
 
limit = 42
i = 42
n = 0
 
while n < limit do
  if i.prime? then
    n += 1
    puts "n = #{n}".ljust(7) + ":" + "#{i.to_s.reverse.scan(/\d{3}|.+/).join(",").reverse}".rjust(19)
    i += i
  else
    i += 1
  end
end
</syntaxhighlight>
Output :
<pre>
n = 1  :                 43
n = 2  :                 89
n = 3  :                179
n = 4  :                359
n = 5  :                719
n = 6  :              1,439
n = 7  :              2,879
n = 8  :              5,779
n = 9  :             11,579
n = 10 :             23,159
n = 11 :             46,327
n = 12 :             92,657
n = 13 :            185,323
n = 14 :            370,661
n = 15 :            741,337
n = 16 :          1,482,707
n = 17 :          2,965,421
n = 18 :          5,930,887
n = 19 :         11,861,791
n = 20 :         23,723,597
n = 21 :         47,447,201
n = 22 :         94,894,427
n = 23 :        189,788,857
n = 24 :        379,577,741
n = 25 :        759,155,483
n = 26 :      1,518,310,967
n = 27 :      3,036,621,941
n = 28 :      6,073,243,889
n = 29 :     12,146,487,779
n = 30 :     24,292,975,649
n = 31 :     48,585,951,311
n = 32 :     97,171,902,629
n = 33 :    194,343,805,267
n = 34 :    388,687,610,539
n = 35 :    777,375,221,081
n = 36 :  1,554,750,442,183
n = 37 :  3,109,500,884,389
n = 38 :  6,219,001,768,781
n = 39 : 12,438,003,537,571
n = 40 : 24,876,007,075,181
n = 41 : 49,752,014,150,467
n = 42 : 99,504,028,301,131
</pre>

=={{header|Scala}}==
Like most other [[wp:en:Block_(programming)|Block structured languages]] (apparently with the exception of Java), Scala's 'for' statement is for the sake of fallibility aka side effect or mutability, limited and doesn't allow either the iteration variable or the step to be modified within the loop body. Both are for serious reasons immutable.
===Demonstrate the best way to accomplish this.===
So instead we use tail recursion here which, with the use of immutable variables and no side effects, has no such restrictions, and we are save.
{{Out}}Best seen running in your browser either by [https://scalafiddle.io/sf/4HJPkBM/1 ScalaFiddle (ES aka JavaScript, non JVM)] or [https://scastie.scala-lang.org/yzqldLOuRriR6ojqLKaYPQ Scastie (remote JVM)].
<syntaxhighlight lang="scala">import scala.annotation.tailrec

object LoopIncrementWithinBody extends App {
  private val (limit, offset) = (42L, 1)

  @tailrec
  private def loop(i: Long, n: Int): Unit = {

    def isPrime(n: Long) =
      n > 1 && ((n & 1) != 0 || n == 2) && (n % 3 != 0 || n == 3) &&
        ((5 to math.sqrt(n).toInt by 2).par forall (n % _ != 0))

    if (n < limit + offset)
      if (isPrime(i)) {
        printf("n = %-2d  %,19d%n".formatLocal(java.util.Locale.GERMANY, n, i))
        loop(i + i + 1, n + 1)
      } else loop(i + 1, n)
  }

  loop(limit, offset)
}</syntaxhighlight>

=={{header|Seed7}}==
<syntaxhighlight lang="seed7">$ include "seed7_05.s7i";
 
const func boolean: isPrime (in integer: number) is func
  result
    var boolean: result is FALSE;
  local
    var integer: count is 2;
  begin
    if number = 2 then
      result := TRUE;
    elsif number > 2 then
      while number rem count <> 0 and count * count <= number do
        incr(count);
      end while;
      result := number rem count <> 0;
    end if;
  end func;

const proc: main is func
  local
    var integer: i is 42;
    var integer: n is 0;
  begin
    for i range 42 to integer.last until n >= 42 do
      if isPrime(i) then
        incr(n);
        writeln("n = " <& n lpad 2 <& i lpad 16);
        i +:= i - 1;
      end if;
    end for;
  end func;</syntaxhighlight>

{{out}}
<pre>
n =  1              43
n =  2              89
n =  3             179
n =  4             359
n =  5             719
n =  6            1439
n =  7            2879
n =  8            5779
n =  9           11579
n = 10           23159
n = 11           46327
n = 12           92657
n = 13          185323
n = 14          370661
n = 15          741337
n = 16         1482707
n = 17         2965421
n = 18         5930887
n = 19        11861791
n = 20        23723597
n = 21        47447201
n = 22        94894427
n = 23       189788857
n = 24       379577741
n = 25       759155483
n = 26      1518310967
n = 27      3036621941
n = 28      6073243889
n = 29     12146487779
n = 30     24292975649
n = 31     48585951311
n = 32     97171902629
n = 33    194343805267
n = 34    388687610539
n = 35    777375221081
n = 36   1554750442183
n = 37   3109500884389
n = 38   6219001768781
n = 39  12438003537571
n = 40  24876007075181
n = 41  49752014150467
n = 42  99504028301131
</pre>

=={{header|Smalltalk}}==
{{works with|Smalltalk/X}}
<syntaxhighlight lang="smalltalk">numFound := 0.
idx := 42.
[:exit |
    idx := idx + 1.
    idx isPrime ifTrue:[
        numFound := numFound + 1.
        '%d %20d\n' printf:{numFound . idx} on:Transcript.
        idx := idx + idx - 1.
        numFound == 42 ifTrue:exit
    ].
] loopWithExit.</syntaxhighlight>
Note: above code uses a public domain printf goodie which is part of many Smalltalk's base libraries; if not present in a particular dialect, use regular print/display/transcribe or whatever is available.
{{out}}
<pre>1                   43
2                   89
3                  179
4                  359
5                  719
6                 1439
7                 2879
8                 5779
9                11579
10                23159
11                46327
12                92657
13               185323
...
36        1554750442183
37        3109500884389
38        6219001768781
39       12438003537571
40       24876007075181
41       49752014150467
42       99504028301131</pre>

=={{header|Standard ML}}==
<syntaxhighlight lang="standard ml">
fun until done change dolast x =
    if done x
      then    dolast x
      else    until done change dolast (change x);       (* iteration/generic loop *)


val isprime = fn n :IntInf.int  =>
let
 fun butlast (_,t)   = t*t > n
 fun divide (n,t)    = n mod t = 0 orelse t*t > n
 fun trymore (n,t)   = (n,t + 2)
in

 n mod 2 <> 0 andalso until divide trymore butlast (n,3)

end;

val loop =  fn () =>
let
 fun butthislast (_,p,_) = rev p 
 fun wegot42 (n,_,_)     = n = 43
 fun trymore (n,p,i)     = if isprime i 
                                   then ( n+1, (n,i)::p , i+i )
                                   else ( n ,  p, i+1)
in

  until wegot42 trymore butthislast  (1,[],42)

end ;

val printp = fn clist:(int*IntInf.int) list =>
 List.app (fn i=>print ((Int.toString (#1 i) )^" : "^ (IntInf.toString (#2 i) )^"\n")) clist ; </syntaxhighlight>
call <pre>
 printp (loop ()) ;
1 : 43
2 : 89
3 : 179
4 : 359
5 : 719
6 : 1439
7 : 2879
8 : 5779
9 : 11579
10 : 23159
11 : 46327
12 : 92657
13 : 185323
14 : 370661
15 : 741337
16 : 1482707
17 : 2965421
18 : 5930887
19 : 11861791
20 : 23723597
21 : 47447201
22 : 94894427
23 : 189788857
24 : 379577741
25 : 759155483
26 : 1518310967
27 : 3036621941
28 : 6073243889
29 : 12146487779
30 : 24292975649
31 : 48585951311
32 : 97171902629
33 : 194343805267
34 : 388687610539
35 : 777375221081
36 : 1554750442183
37 : 3109500884389
38 : 6219001768781
39 : 12438003537571
40 : 24876007075181
41 : 49752014150467
42 : 99504028301131</pre>

=={{header|Tcl}}==
Inspired by Java and Kotlin variants.

Tcl allows modifying the loop variable. Everything can be implemented straightforward.
<syntaxhighlight lang="tcl">proc isPrime n {
  if {[expr $n % 2] == 0} {
    return [expr $n == 2]
  }
  if {[expr $n % 3] == 0} {
    return [expr $n == 3]
  }
  for {set d 5} {[expr $d * $d] <= $n} {incr d 4} {
    if {[expr $n % $d] == 0} {return 0}
    incr d 2
    if {[expr $n % $d] == 0} {return 0}
  }
  return 1
}

set LIMIT 42

for {set i $LIMIT; set n 0} {$n < $LIMIT} {incr i} {
  if [isPrime $i] {
    incr n
    puts "n=$n, i=$i"
    incr i [expr $i -1]
  }
}</syntaxhighlight>
{{Out}}
<pre>n=1, i=43
n=2, i=89
n=3, i=179
n=4, i=359
n=5, i=719
n=6, i=1439
n=7, i=2879
n=8, i=5779
n=9, i=11579
n=10, i=23159
n=11, i=46327
n=12, i=92657
n=13, i=185323
n=14, i=370661
n=15, i=741337
n=16, i=1482707
n=17, i=2965421
n=18, i=5930887
n=19, i=11861791
n=20, i=23723597
n=21, i=47447201
n=22, i=94894427
n=23, i=189788857
n=24, i=379577741
n=25, i=759155483
n=26, i=1518310967
n=27, i=3036621941
n=28, i=6073243889
n=29, i=12146487779
n=30, i=24292975649
n=31, i=48585951311
n=32, i=97171902629
n=33, i=194343805267
n=34, i=388687610539
n=35, i=777375221081
n=36, i=1554750442183
n=37, i=3109500884389
n=38, i=6219001768781
n=39, i=12438003537571
n=40, i=24876007075181
n=41, i=49752014150467
n=42, i=99504028301131</pre>

=={{header|VBA}}==
Visual Basic for Application (VBA) allows to modify the index inside the loop.
{{trans|Visual Basic .NET}}
{{works with|VBA|VBA Excel 2013}}
<syntaxhighlight lang="vb">    Sub Main()
        'Loops Increment loop index within loop body - 17/07/2018
        Dim imax, i As Integer
        Dim n As Currency
        imax = 42
        i = 0: n = 42
        Do While i < imax
            If IsPrime(n) Then
                i = i + 1
                Debug.Print ("i=" & RightX(i, 2) & " : " & RightX(Format(n, "#,##0"), 20))
                n = n + n - 1
            End If
            n = n + 1
        Loop
    End Sub 'Main

    Function IsPrime(n As Currency)
        Dim i As Currency
        If n = 2 Or n = 3 Then
            IsPrime = True
        ElseIf ModX(n, 2) = 0 Or ModX(n, 3) = 0 Then
            IsPrime = False
        Else
            i = 5
            Do While i * i <= n
                If ModX(n, i) = 0 Or ModX(n, i + 2) = 0 Then
                    IsPrime = False
                    Exit Function
                End If
                i = i + 6
            Loop
            IsPrime = True
        End If
    End Function 'IsPrime

    Function ModX(a As Currency, b As Currency) As Currency
        ModX = a - Int(a / b) * b
    End Function 'ModX
    
    Function RightX(c, n)
        RightX = Right(Space(n) & c, n)
    End Function 'RightX</syntaxhighlight>
{{out}}
<pre style="height:60ex">
i= 1 :                   43
i= 2 :                   89
i= 3 :                  179
i= 4 :                  359
i= 5 :                  719
i= 6 :                1,439
i= 7 :                2,879
i= 8 :                5,779
i= 9 :               11,579
i=10 :               23,159
i=11 :               46,327
i=12 :               92,657
i=13 :              185,323
i=14 :              370,661
i=15 :              741,337
i=16 :            1,482,707
i=17 :            2,965,421
i=18 :            5,930,887
i=19 :           11,861,791
i=20 :           23,723,597
i=21 :           47,447,201
i=22 :           94,894,427
i=23 :          189,788,857
i=24 :          379,577,741
i=25 :          759,155,483
i=26 :        1,518,310,967
i=27 :        3,036,621,941
i=28 :        6,073,243,889
i=29 :       12,146,487,779
i=30 :       24,292,975,649
i=31 :       48,585,951,311
i=32 :       97,171,902,629
i=33 :      194,343,805,267
i=34 :      388,687,610,539
i=35 :      777,375,221,081
i=36 :    1,554,750,442,183
i=37 :    3,109,500,884,389
i=38 :    6,219,001,768,781
i=39 :   12,438,003,537,571
i=40 :   24,876,007,075,181
i=41 :   49,752,014,150,467
i=42 :   99,504,028,301,131</pre>

=={{header|Visual Basic .NET}}==
Visual Basic .Net allows to modify the index inside the loop.
{{trans|Visual Basic}}
{{works with|Visual Basic .NET|2013}}
<syntaxhighlight lang="vbnet">Module LoopsIliwlb

    Sub Main()
        'Loops Increment loop index within loop body - 17/07/2018
        Dim imax, i As Int32
        Dim n As Int64
        imax = 42
        i = 0 : n = 42
        While i < imax
            If IsPrime(n) Then
                i = i + 1
                Console.WriteLine("i=" & RightX(i, 2) & " : " & RightX(Format(n, "#,##0"), 20))
                n = n + n - 1
            End If
            n = n + 1
        End While
    End Sub

    Function IsPrime(n As Int64)
        Dim i As Int64
        If n = 2 Or n = 3 Then
            IsPrime = True
        ElseIf (n Mod 2) = 0 Or (n Mod 3) = 0 Then
            IsPrime = False
        Else
            i = 5
            While i * i <= n
                If (n Mod i) = 0 Or (n Mod (i + 2)) = 0 Then
                    IsPrime = False
                    Exit Function
                End If
                i = i + 6
            End While
            IsPrime = True
        End If
    End Function 'IsPrime

    Function RightX(c, n)
        RightX = Right(Space(n) & c, n)
    End Function

End Module</syntaxhighlight>
{{out}}
<pre style="height:60ex">i= 1 :                   43
i= 2 :                   89
i= 3 :                  179
i= 4 :                  359
i= 5 :                  719
i= 6 :                1,439
i= 7 :                2,879
i= 8 :                5,779
i= 9 :               11,579
i=10 :               23,159
i=11 :               46,327
i=12 :               92,657
i=13 :              185,323
i=14 :              370,661
i=15 :              741,337
i=16 :            1,482,707
i=17 :            2,965,421
i=18 :            5,930,887
i=19 :           11,861,791
i=20 :           23,723,597
i=21 :           47,447,201
i=22 :           94,894,427
i=23 :          189,788,857
i=24 :          379,577,741
i=25 :          759,155,483
i=26 :        1,518,310,967
i=27 :        3,036,621,941
i=28 :        6,073,243,889
i=29 :       12,146,487,779
i=30 :       24,292,975,649
i=31 :       48,585,951,311
i=32 :       97,171,902,629
i=33 :      194,343,805,267
i=34 :      388,687,610,539
i=35 :      777,375,221,081
i=36 :    1,554,750,442,183
i=37 :    3,109,500,884,389
i=38 :    6,219,001,768,781
i=39 :   12,438,003,537,571
i=40 :   24,876,007,075,181
i=41 :   49,752,014,150,467
i=42 :   99,504,028,301,131</pre>

=={{header|V (Vlang)}}==
{{trans|go}}
<syntaxhighlight lang="v (vlang)">fn is_prime(n u64) bool {
    if n % 2 == 0 {
        return n == 2
    }
    if n % 3 == 0 {
        return n == 3
    }
    mut d := u64(5)
    for d * d <= n {
        if n % d == 0 {
            return false
        }
        d += 2
        if n % d == 0 {
            return false
        } 
        d += 4
    }
    return true
}
const limit = 42
fn main() {
    for i, n := u64(limit), 0; n<limit; i++ {
        if is_prime(i) {
            n++
            println("n = ${n:-2}  ${i:19}")
            i += i - 1
        }
    }
}</syntaxhighlight>

{{out}}
<pre>
Same as Kotlin entry
</pre>

=={{header|Wren}}==
{{libheader|Wren-fmt}}
Although it might appear as though one can change the index variable within a ''for'' loop, it does in fact change a local copy of the variable and the iteration is not affected at all. Consequently, the only way to complete this task in Wren is to use a ''while'' loop.
<syntaxhighlight lang="ecmascript">import "/fmt" for Fmt

var isPrime = Fn.new { |n|
    if (n < 2 || !n.isInteger) return false
    if (n%2 == 0) return n == 2
    if (n%3 == 0) return n == 3
    var d = 5
    while (d*d <= n) {
        if (n%d == 0) return false
        d = d + 2
        if (n%d == 0) return false
        d = d + 4
    }
    return true
}

var count = 0
var i = 42
while (count < 42) {
    if (isPrime.call(i)) {
        count = count + 1
        System.print("%(Fmt.d(2, count)): %(Fmt.dc(18, i))")
        i = 2 * i - 1        
    }
    i = i + 1
}</syntaxhighlight>

{{out}}
<pre>
 1:                 43
 2:                 89
 3:                179
 4:                359
 5:                719
 6:              1,439
 7:              2,879
 8:              5,779
 9:             11,579
10:             23,159
11:             46,327
12:             92,657
13:            185,323
14:            370,661
15:            741,337
16:          1,482,707
17:          2,965,421
18:          5,930,887
19:         11,861,791
20:         23,723,597
21:         47,447,201
22:         94,894,427
23:        189,788,857
24:        379,577,741
25:        759,155,483
26:      1,518,310,967
27:      3,036,621,941
28:      6,073,243,889
29:     12,146,487,779
30:     24,292,975,649
31:     48,585,951,311
32:     97,171,902,629
33:    194,343,805,267
34:    388,687,610,539
35:    777,375,221,081
36:  1,554,750,442,183
37:  3,109,500,884,389
38:  6,219,001,768,781
39: 12,438,003,537,571
40: 24,876,007,075,181
41: 49,752,014,150,467
42: 99,504,028,301,131
</pre>

=={{header|Yabasic}}==
<syntaxhighlight lang="yabasic">i = 42
counter = 0
while counter < 42
    if isPrime(i) then
        counter = counter + 1
        print "n = ", counter, chr$(9), i
        i = i + i - 1
    end if
    i = i + 1
wend
end

sub isPrime(v)
    if v < 2  return False
    if mod(v, 2) = 0  return v = 2
    if mod(v, 3) = 0  return v = 3
    d = 5
    while d * d <= v
        if mod(v, d) = 0 then return False else d = d + 2 : fi
    wend
    return True
end sub</syntaxhighlight>

=={{header|zkl}}==
Uses libGMP (GNU MP Bignum Library) for easy prime detection
rather than write that bit of code and pollute this solution.
<syntaxhighlight lang="zkl">var [const] BN=Import("zklBigNum");  // libGMP
n,p := 1,BN(42);
do{
   if(p.probablyPrime()){ println("n = %2d %,20d".fmt(n,p)); p.add(p); n+=1; }
   p.add(1); 
}while(n<=42);</syntaxhighlight>
zkl loop variables are iterators that don't allow direct manipulation of
their underlying source. The compiler names these iterators __<index>Walker.
However, by using the look ahead stack, we can keep the iterator from
advancing through the source.
<syntaxhighlight lang="zkl">p:=BN(42);
foreach n in ([1..42]){
   if(p.probablyPrime()){ println("n = %2d %,20d".fmt(n,p)); p.add(p); }
   else{ p.add(1); __nWalker.push(n); }  // p not prime, don't advance n
}</syntaxhighlight>
{{out}}
<pre style="height:35ex">
n =  1                   43
n =  2                   89
n =  3                  179
n =  4                  359
n =  5                  719
n =  6                1,439
n =  7                2,879
n =  8                5,779
n =  9               11,579
n = 10               23,159
n = 11               46,327
n = 12               92,657
n = 13              185,323
n = 14              370,661
n = 15              741,337
n = 16            1,482,707
n = 17            2,965,421
n = 18            5,930,887
n = 19           11,861,791
n = 20           23,723,597
n = 21           47,447,201
n = 22           94,894,427
n = 23          189,788,857
n = 24          379,577,741
n = 25          759,155,483
n = 26        1,518,310,967
n = 27        3,036,621,941
n = 28        6,073,243,889
n = 29       12,146,487,779
n = 30       24,292,975,649
n = 31       48,585,951,311
n = 32       97,171,902,629
n = 33      194,343,805,267
n = 34      388,687,610,539
n = 35      777,375,221,081
n = 36    1,554,750,442,183
n = 37    3,109,500,884,389
n = 38    6,219,001,768,781
n = 39   12,438,003,537,571
n = 40   24,876,007,075,181
n = 41   49,752,014,150,467
n = 42   99,504,028,301,131
</pre>