Rosetta Code

Iccanobif primes

Revision as of 02:20, 29 April 2023 by Wherrera (talk | contribs) (→‎{{header|Python}})

Iccanobif primes are prime numbers that, when reversed, are a Fibonacci number.

Iccanobif primes is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.


Task
  • Find and display the first 10 iccanobif primes.


Stretch
  • Find and display the digit count of the next 15 iccanobif primes.


See also


ALGOL 68

BEGIN # show the first 10 prime Iccanobif (reversed Fibonacci) numbers       #
    # returns n with the digits reversed                                     #
    OP REVERSE = ( INT n )INT:
       BEGIN
            INT reverse := 0;
            INT v       := ABS n;
            WHILE v > 0 DO
                reverse *:= 10 +:= v MOD 10;
                v OVERAB 10
            OD;
            reverse * SIGN n
       END # REVERSE # ;
    # returns TRUE if n is prime, FALSE otherwise - uses trial division      #
    PROC is prime = ( LONG INT n )BOOL:
         IF   n < 3       THEN n = 2
         ELIF n MOD 3 = 0 THEN n = 3
         ELIF NOT ODD n   THEN FALSE
         ELSE
             BOOL is a prime := TRUE;
             INT  f          := 5;
             INT  f2         := 25;
             INT  to next    := 24;
             WHILE f2 <= n AND is a prime DO
                 is a prime := n MOD f /= 0;
                 f         +:= 2;
                 f2        +:= to next;
                 to next   +:= 8
             OD;
             is a prime
         FI # is prime # ;
    # task                                                                   #
    INT p count := 0;
    INT prev    := 0;
    INT curr    := 1;
    WHILE p count < 10 DO
        INT next = prev + curr;
        prev    := curr;
        curr    := next;
        INT rev := REVERSE curr;
        IF is prime( rev ) THEN
            # have a prime iccanobif number #
            p count +:= 1;
            print( ( " ", whole( rev, 0 ) ) )
        FI
    OD
END
Output:
 2 3 5 31 43 773 7951 64901 52057 393121

Python

Translation of: Wren
""" rosettacode.org/wiki/Iccanobif_primes """

from sympy import isprime


def iccanobifs(wanted):
    """ Print the series of iccanobif prime numbers up to wanted """
    fib, prev, prevprev, fcount = 0, 1, 0, 0
    print('First 30 Iccanobif primes:')
    while fcount < wanted:
        fib = prev + prevprev
        prevprev = prev
        prev = fib
        dig = [int(c) for c in str(fib)]
        candidate = sum(n * 10**i for i, n in enumerate(dig))
        if isprime(candidate):
            fcount += 1
            dlen = len(str(candidate))
            if dlen < 90:
                print(candidate, f"({dlen} digit{'' if dlen == 1 else 's'})")
            else:
                s = str(candidate)
                print(s[:30], "...", s[-29:], f'({dlen} digits)')


iccanobifs(30)
Output:
First 30 Iccanobif primes:
2 (1 digit)
3 (1 digit)
5 (1 digit)
31 (2 digits)
43 (2 digits)
773 (3 digits)
7951 (4 digits)
64901 (5 digits)
52057 (5 digits)
393121 (6 digits)
56577108676171 (14 digits)
940647607443258103531 (21 digits)
5237879497657222310489731409575442761 (37 digits)
9026258083384996860449366072142307801963 (40 digits)
19900335674812302969315720344396951060628175943800862267761734431012073266446403 (80 digits)
778411373629674799853537498387 ... 06414225852312097783685331923 (104 digits)
377225859015676041888905465423 ... 42640418929174997072830756131 (137 digits)
757361938948761315956093082097 ... 05343825250767238644714305761 (330 digits)
178903368473328376208382371633 ... 39766460613175300695235035913 (406 digits)
923271631017291153059188123189 ... 39342926827061468856047302507 (409 digits)
504201578106980562530763299184 ... 34364678167335124247362214481 (503 digits)
305110124747393800923565587415 ... 27995099969296158361330018201 (888 digits)
468185470426936945550027667953 ... 73037342708664543144645856321 (1020 digits)
871013478530378198843208828928 ... 72170748420128396998865227391 (1122 digits)
174516560225437653361964336594 ... 30820185220100243761843652461 (1911 digits)
489893405662883994748316933771 ... 74664296802930339234215909399 (1947 digits)
127469276849582096547381559312 ... 19580690153436989647994940101 (2283 digits)
357468265826587510126602192036 ... 69346589325010735912438195633 (3727 digits)
879871752812976577066489068488 ... 66056251048748727893681871587 (4270 digits)
^C (took too long)

Raku

sub abbr ($_) { (.chars < 41 ?? $_ !! .substr(0,20) ~ '..' ~ .substr(*-20)) ~ " (digits: {.chars})" }

say (++$).fmt('%2d') ~ ': ' ~ .flip.&abbr for (lazy (1,1,*+*…*).hyper.grep: {.flip.is-prime})[^25];
Output:
 1: 2 (digits: 1)
 2: 3 (digits: 1)
 3: 5 (digits: 1)
 4: 31 (digits: 2)
 5: 43 (digits: 2)
 6: 773 (digits: 3)
 7: 7951 (digits: 4)
 8: 64901 (digits: 5)
 9: 52057 (digits: 5)
10: 393121 (digits: 6)
11: 56577108676171 (digits: 14)
12: 940647607443258103531 (digits: 21)
13: 5237879497657222310489731409575442761 (digits: 37)
14: 9026258083384996860449366072142307801963 (digits: 40)
15: 19900335674812302969..34431012073266446403 (digits: 80)
16: 77841137362967479985..52312097783685331923 (digits: 104)
17: 37722585901567604188..29174997072830756131 (digits: 137)
18: 75736193894876131595..50767238644714305761 (digits: 330)
19: 17890336847332837620..13175300695235035913 (digits: 406)
20: 92327163101729115305..27061468856047302507 (digits: 409)
21: 50420157810698056253..67335124247362214481 (digits: 503)
22: 30511012474739380092..69296158361330018201 (digits: 888)
23: 46818547042693694555..08664543144645856321 (digits: 1020)
24: 87101347853037819884..20128396998865227391 (digits: 1122)
25: 17451656022543765336..20100243761843652461 (digits: 1911)
26: 48989340566288399474..02930339234215909399 (digits: 1947)
27: 12746927684958209654..53436989647994940101 (digits: 2283)
28: 35746826582658751012..25010735912438195633 (digits: 3727)
29: 87987175281297657706..48748727893681871587 (digits: 4270)
30: 81807376367113798363..13687506007959668569 (digits: 10527)

Wren

Library: Wren-gmp
Library: Wren-fmt
import "./gmp" for Mpz
import "./fmt" for Fmt

var fib = Mpz.new()
var p = Mpz.new()
var prev = Mpz.zero
var curr = Mpz.one
var count = 0
System.print("First 30 Iccanobif primes:")
while (count < 30) {
    fib.add(curr, prev)
    var fs = fib.toString
    p.setStr(fs[-1..0])
    if (p.probPrime(15) > 0) {
        count =  count + 1
        var pc = p.toString.count
        Fmt.print("$2d: $20a ($d digits)", count, p, pc)
    }
    prev.set(curr)
    curr.set(fib)
}
Output:
First 27 Iccanobif primes:
 1: 2 (1 digits)
 2: 3 (1 digits)
 3: 5 (1 digits)
 4: 31 (2 digits)
 5: 43 (2 digits)
 6: 773 (3 digits)
 7: 7951 (4 digits)
 8: 64901 (5 digits)
 9: 52057 (5 digits)
10: 393121 (6 digits)
11: 56577108676171 (14 digits)
12: 940647607443258103531 (21 digits)
13: 5237879497657222310489731409575442761 (37 digits)
14: 9026258083384996860449366072142307801963 (40 digits)
15: 19900335674812302969...34431012073266446403 (80 digits)
16: 77841137362967479985...52312097783685331923 (104 digits)
17: 37722585901567604188...29174997072830756131 (137 digits)
18: 75736193894876131595...50767238644714305761 (330 digits)
19: 17890336847332837620...13175300695235035913 (406 digits)
20: 92327163101729115305...27061468856047302507 (409 digits)
21: 50420157810698056253...67335124247362214481 (503 digits)
22: 30511012474739380092...69296158361330018201 (888 digits)
23: 46818547042693694555...08664543144645856321 (1020 digits)
24: 87101347853037819884...20128396998865227391 (1122 digits)
25: 17451656022543765336...20100243761843652461 (1911 digits)
26: 48989340566288399474...02930339234215909399 (1947 digits)
27: 12746927684958209654...53436989647994940101 (2283 digits)
28: 35746826582658751012...25010735912438195633 (3727 digits)
29: 87987175281297657706...48748727893681871587 (4270 digits)
30: 81807376367113798363...13687506007959668569 (10527 digits)
Retrieved from "https://rosettacode.org/wiki/Iccanobif_primes?oldid=341150"