Attractive numbers

From Rosetta Code
Task
Attractive numbers
You are encouraged to solve this task according to the task description, using any language you may know.

A number is an   attractive number   if the number of its prime factors (whether distinct or not) is also prime.


Example

The number   20,   whose prime decomposition is   2 × 2 × 5,   is an   attractive number   because the number of its prime factors   (3)   is also prime.


Task

Show sequence items up to   120.


Reference



AWK[edit]

 
# syntax: GAWK -f ATTRACTIVE_NUMBERS.AWK
# converted from C
BEGIN {
limit = 120
printf("attractive numbers from 1-%d:\n",limit)
for (i=1; i<=limit; i++) {
n = count_prime_factors(i)
if (is_prime(n)) {
printf("%d ",i)
}
}
printf("\n")
exit(0)
}
function count_prime_factors(n, count,f) {
f = 2
if (n == 1) { return(0) }
if (is_prime(n)) { return(1) }
while (1) {
if (!(n % f)) {
count++
n /= f
if (n == 1) { return(count) }
if (is_prime(n)) { f = n }
}
else if (f >= 3) { f += 2 }
else { f = 3 }
}
}
function is_prime(x, i) {
if (x <= 1) {
return(0)
}
for (i=2; i<=int(sqrt(x)); i++) {
if (x % i == 0) {
return(0)
}
}
return(1)
}
 
Output:
attractive numbers from 1-120:
4 6 8 9 10 12 14 15 18 20 21 22 25 26 27 28 30 32 33 34 35 38 39 42 44 45 46 48 49 50 51 52 55 57 58 62 63 65 66 68 69 70 72 74 75 76 77 78 80 82 85 86 87 91 92 93 94 95 98 99 102 105 106 108 110 111 112 114 115 116 117 118 119 120

C[edit]

Translation of: Go
#include <stdio.h>
 
#define TRUE 1
#define FALSE 0
#define MAX 120
 
typedef int bool;
 
bool is_prime(int n) {
int d = 5;
if (n < 2) return FALSE;
if (!(n % 2)) return n == 2;
if (!(n % 3)) return n == 3;
while (d *d <= n) {
if (!(n % d)) return FALSE;
d += 2;
if (!(n % d)) return FALSE;
d += 4;
}
return TRUE;
}
 
int count_prime_factors(int n) {
int count = 0, f = 2;
if (n == 1) return 0;
if (is_prime(n)) return 1;
while (TRUE) {
if (!(n % f)) {
count++;
n /= f;
if (n == 1) return count;
if (is_prime(n)) f = n;
}
else if (f >= 3) f += 2;
else f = 3;
}
}
 
int main() {
int i, n, count = 0;
printf("The attractive numbers up to and including %d are:\n", MAX);
for (i = 1; i <= MAX; ++i) {
n = count_prime_factors(i);
if (is_prime(n)) {
printf("%4d", i);
if (!(++count % 20)) printf("\n");
}
}
printf("\n");
return 0;
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

C++[edit]

Translation of: C
#include <iostream>
#include <iomanip>
 
#define MAX 120
 
using namespace std;
 
bool is_prime(int n) {
if (n < 2) return false;
if (!(n % 2)) return n == 2;
if (!(n % 3)) return n == 3;
int d = 5;
while (d *d <= n) {
if (!(n % d)) return false;
d += 2;
if (!(n % d)) return false;
d += 4;
}
return true;
}
 
int count_prime_factors(int n) {
if (n == 1) return 0;
if (is_prime(n)) return 1;
int count = 0, f = 2;
while (true) {
if (!(n % f)) {
count++;
n /= f;
if (n == 1) return count;
if (is_prime(n)) f = n;
}
else if (f >= 3) f += 2;
else f = 3;
}
}
 
int main() {
cout << "The attractive numbers up to and including " << MAX << " are:" << endl;
for (int i = 1, count = 0; i <= MAX; ++i) {
int n = count_prime_factors(i);
if (is_prime(n)) {
cout << setw(4) << i;
if (!(++count % 20)) cout << endl;
}
}
cout << endl;
return 0;
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

C#[edit]

Translation of: D
using System;
 
namespace AttractiveNumbers {
class Program {
const int MAX = 120;
 
static bool IsPrime(int n) {
if (n < 2) return false;
if (n % 2 == 0) return n == 2;
if (n % 3 == 0) return n == 3;
int d = 5;
while (d * d <= n) {
if (n % d == 0) return false;
d += 2;
if (n % d == 0) return false;
d += 4;
}
return true;
}
 
static int PrimeFactorCount(int n) {
if (n == 1) return 0;
if (IsPrime(n)) return 1;
int count = 0;
int f = 2;
while (true) {
if (n % f == 0) {
count++;
n /= f;
if (n == 1) return count;
if (IsPrime(n)) f = n;
} else if (f >= 3) {
f += 2;
} else {
f = 3;
}
}
}
 
static void Main(string[] args) {
Console.WriteLine("The attractive numbers up to and including {0} are:", MAX);
int i = 1;
int count = 0;
while (i <= MAX) {
int n = PrimeFactorCount(i);
if (IsPrime(n)) {
Console.Write("{0,4}", i);
if (++count % 20 == 0) Console.WriteLine();
}
++i;
}
Console.WriteLine();
}
}
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

D[edit]

Translation of: C++
import std.stdio;
 
enum MAX = 120;
 
bool isPrime(int n) {
if (n < 2) return false;
if (n % 2 == 0) return n == 2;
if (n % 3 == 0) return n == 3;
int d = 5;
while (d * d <= n) {
if (n % d == 0) return false;
d += 2;
if (n % d == 0) return false;
d += 4;
}
return true;
}
 
int primeFactorCount(int n) {
if (n == 1) return 0;
if (isPrime(n)) return 1;
int count;
int f = 2;
while (true) {
if (n % f == 0) {
count++;
n /= f;
if (n == 1) return count;
if (isPrime(n)) f = n;
} else if (f >= 3) {
f += 2;
} else {
f = 3;
}
}
}
 
void main() {
writeln("The attractive numbers up to and including ", MAX, " are:");
int i = 1;
int count;
while (i <= MAX) {
int n = primeFactorCount(i);
if (isPrime(n)) {
writef("%4d", i);
if (++count % 20 == 0) writeln;
}
++i;
}
writeln;
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Factor[edit]

Works with: Factor version 0.99
USING: formatting grouping io math.primes math.primes.factors
math.ranges sequences ;
 
"The attractive numbers up to and including 120 are:" print
120 [1,b] [ factors length prime? ] filter 20 <groups>
[ [ "%4d" printf ] each nl ] each
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

FreeBASIC[edit]

Translation of: D
 
Const limite = 120
 
Declare Function esPrimo(n As Integer) As Boolean
Declare Function ContandoFactoresPrimos(n As Integer) As Integer
 
Function esPrimo(n As Integer) As Boolean
If n < 2 Then Return false
If n Mod 2 = 0 Then Return n = 2
If n Mod 3 = 0 Then Return n = 3
Dim As Integer d = 5
While d * d <= n
If n Mod d = 0 Then Return false
d += 2
If n Mod d = 0 Then Return false
d += 4
Wend
Return true
End Function
 
Function ContandoFactoresPrimos(n As Integer) As Integer
If n = 1 Then Return false
If esPrimo(n) Then Return true
Dim As Integer f = 2, contar = 0
While true
If n Mod f = 0 Then
contar += 1
n = n / f
If n = 1 Then Return contar
If esPrimo(n) Then f = n
Elseif f >= 3 Then
f += 2
Else
f = 3
End If
Wend
End Function
 
' Mostrar la sucencia de números atractivos hasta 120.
Dim As Integer i = 1, longlinea = 0
 
Print "Los numeros atractivos hasta e incluyendo"; limite; " son: "
While i <= limite
Dim As Integer n = ContandoFactoresPrimos(i)
If esPrimo(n) Then
Print Using "####"; i;
longlinea += 1: If longlinea Mod 20 = 0 Then Print ""
End If
i += 1
Wend
End
 
Output:
Los numeros atractivos hasta e incluyendo 120 son:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Go[edit]

Simple functions to test for primality and to count prime factors suffice here.

package main
 
import "fmt"
 
func isPrime(n int) bool {
switch {
case n < 2:
return false
case n%2 == 0:
return n == 2
case n%3 == 0:
return n == 3
default:
d := 5
for d*d <= n {
if n%d == 0 {
return false
}
d += 2
if n%d == 0 {
return false
}
d += 4
}
return true
}
}
 
func countPrimeFactors(n int) int {
switch {
case n == 1:
return 0
case isPrime(n):
return 1
default:
count, f := 0, 2
for {
if n%f == 0 {
count++
n /= f
if n == 1 {
return count
}
if isPrime(n) {
f = n
}
} else if f >= 3 {
f += 2
} else {
f = 3
}
}
return count
}
}
 
func main() {
const max = 120
fmt.Println("The attractive numbers up to and including", max, "are:")
count := 0
for i := 1; i <= max; i++ {
n := countPrimeFactors(i)
if isPrime(n) {
fmt.Printf("%4d", i)
count++
if count % 20 == 0 {
fmt.Println()
}
}
}
fmt.Println()
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Groovy[edit]

Translation of: Java
class AttractiveNumbers {
static boolean isPrime(int n) {
if (n < 2) return false
if (n % 2 == 0) return n == 2
if (n % 3 == 0) return n == 3
int d = 5
while (d * d <= n) {
if (n % d == 0) return false
d += 2
if (n % d == 0) return false
d += 4
}
return true
}
 
static int countPrimeFactors(int n) {
if (n == 1) return 0
if (isPrime(n)) return 1
int count = 0, f = 2
while (true) {
if (n % f == 0) {
count++
n /= f
if (n == 1) return count
if (isPrime(n)) f = n
} else if (f >= 3) f += 2
else f = 3
}
}
 
static void main(String[] args) {
final int max = 120
printf("The attractive numbers up to and including %d are:\n", max)
int count = 0
for (int i = 1; i <= max; ++i) {
int n = countPrimeFactors(i)
if (isPrime(n)) {
printf("%4d", i)
if (++count % 20 == 0) println()
}
}
println()
}
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Haskell[edit]

import Data.Numbers.Primes
import Data.Bool (bool)
 
attractiveNumbers :: [Integer]
attractiveNumbers =
[1 ..] >>= (bool [] . return) <*> (isPrime . length . primeFactors)
 
main :: IO ()
main = print $ takeWhile (<= 120) attractiveNumbers

Or equivalently, as a list comprehension:

import Data.Numbers.Primes
 
attractiveNumbers :: [Integer]
attractiveNumbers =
[ x
| x <- [1 ..]
, isPrime (length (primeFactors x)) ]
 
main :: IO ()
main = print $ takeWhile (<= 120) attractiveNumbers

Or simply:

import Data.Numbers.Primes
 
attractiveNumbers :: [Integer]
attractiveNumbers =
filter
(isPrime . length . primeFactors)
[1 ..]
 
main :: IO ()
main = print $ takeWhile (<= 120) attractiveNumbers
Output:
[4,6,8,9,10,12,14,15,18,20,21,22,25,26,27,28,30,32,33,34,35,38,39,42,44,45,46,48,49,50,51,52,55,57,58,62,63,65,66,68,69,70,72,74,75,76,77,78,80,82,85,86,87,91,92,93,94,95,98,99,102,105,106,108,110,111,112,114,115,116,117,118,119,120]

Java[edit]

Translation of: C
public class Attractive {
 
static boolean is_prime(int n) {
if (n < 2) return false;
if (n % 2 == 0) return n == 2;
if (n % 3 == 0) return n == 3;
int d = 5;
while (d *d <= n) {
if (n % d == 0) return false;
d += 2;
if (n % d == 0) return false;
d += 4;
}
return true;
}
 
static int count_prime_factors(int n) {
if (n == 1) return 0;
if (is_prime(n)) return 1;
int count = 0, f = 2;
while (true) {
if (n % f == 0) {
count++;
n /= f;
if (n == 1) return count;
if (is_prime(n)) f = n;
}
else if (f >= 3) f += 2;
else f = 3;
}
}
 
public static void main(String[] args) {
final int max = 120;
System.out.printf("The attractive numbers up to and including %d are:\n", max);
for (int i = 1, count = 0; i <= max; ++i) {
int n = count_prime_factors(i);
if (is_prime(n)) {
System.out.printf("%4d", i);
if (++count % 20 == 0) System.out.println();
}
}
System.out.println();
}
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Julia[edit]

using Primes
 
# oneliner is println("The attractive numbers from 1 to 120 are:\n", filter(x -> isprime(sum(values(factor(x)))), 1:120))
 
isattractive(n) = isprime(sum(values(factor(n))))
 
printattractive(m, n) = println("The attractive numbers from $m to $n are:\n", filter(isattractive, m:n))
 
printattractive(1, 120)
 
Output:
The attractive numbers from 1 to 120 are:
[4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120]

Kotlin[edit]

Translation of: Go
// Version 1.3.21
 
const val MAX = 120
 
fun isPrime(n: Int) : Boolean {
if (n < 2) return false
if (n % 2 == 0) return n == 2
if (n % 3 == 0) return n == 3
var d : Int = 5
while (d * d <= n) {
if (n % d == 0) return false
d += 2
if (n % d == 0) return false
d += 4
}
return true
}
 
fun countPrimeFactors(n: Int) =
when {
n == 1 -> 0
isPrime(n) -> 1
else -> {
var nn = n
var count = 0
var f = 2
while (true) {
if (nn % f == 0) {
count++
nn /= f
if (nn == 1) break
if (isPrime(nn)) f = nn
} else if (f >= 3) {
f += 2
} else {
f = 3
}
}
count
}
}
 
fun main() {
println("The attractive numbers up to and including $MAX are:")
var count = 0
for (i in 1..MAX) {
val n = countPrimeFactors(i)
if (isPrime(n)) {
System.out.printf("%4d", i)
if (++count % 20 == 0) println()
}
}
println()
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

LLVM[edit]

; This is not strictly LLVM, as it uses the C library function "printf".
; LLVM does not provide a way to print values, so the alternative would be
; to just load the string into memory, and that would be boring.
 
$"ATTRACTIVE_STR" = comdat any
$"FORMAT_NUMBER" = comdat any
$"NEWLINE_STR" = comdat any
 
@"ATTRACTIVE_STR" = linkonce_odr unnamed_addr constant [52 x i8] c"The attractive numbers up to and including %d are:\0A\00", comdat, align 1
@"FORMAT_NUMBER" = linkonce_odr unnamed_addr constant [4 x i8] c"%4d\00", comdat, align 1
@"NEWLINE_STR" = linkonce_odr unnamed_addr constant [2 x i8] c"\0A\00", comdat, align 1
 
;--- The declaration for the external C printf function.
declare i32 @printf(i8*, ...)
 
; Function Attrs: noinline nounwind optnone uwtable
define zeroext i1 @is_prime(i32) #0 {
%2 = alloca i1, align 1 ;-- allocate return value
%3 = alloca i32, align 4 ;-- allocate n
%4 = alloca i32, align 4 ;-- allocate d
store i32 %0, i32* %3, align 4 ;-- store local copy of n
store i32 5, i32* %4, align 4 ;-- store 5 in d
%5 = load i32, i32* %3, align 4 ;-- load n
%6 = icmp slt i32 %5, 2 ;-- n < 2
br i1 %6, label %nlt2, label %niseven
 
nlt2:
store i1 false, i1* %2, align 1 ;-- store false in return value
br label %exit
 
niseven:
%7 = load i32, i32* %3, align 4 ;-- load n
%8 = srem i32 %7, 2 ;-- n % 2
%9 = icmp ne i32 %8, 0 ;-- (n % 2) != 0
br i1 %9, label %odd, label %even
 
even:
%10 = load i32, i32* %3, align 4 ;-- load n
%11 = icmp eq i32 %10, 2 ;-- n == 2
store i1 %11, i1* %2, align 1 ;-- store (n == 2) in return value
br label %exit
 
odd:
%12 = load i32, i32* %3, align 4 ;-- load n
%13 = srem i32 %12, 3 ;-- n % 3
%14 = icmp ne i32 %13, 0 ;-- (n % 3) != 0
br i1 %14, label %loop, label %div3
 
div3:
%15 = load i32, i32* %3, align 4 ;-- load n
%16 = icmp eq i32 %15, 3 ;-- n == 3
store i1 %16, i1* %2, align 1 ;-- store (n == 3) in return value
br label %exit
 
loop:
%17 = load i32, i32* %4, align 4 ;-- load d
%18 = load i32, i32* %4, align 4 ;-- load d
%19 = mul nsw i32 %17, %18 ;-- d * d
%20 = load i32, i32* %3, align 4 ;-- load n
%21 = icmp sle i32 %19, %20 ;-- (d * d) <= n
br i1 %21, label %first, label %prime
 
first:
%22 = load i32, i32* %3, align 4 ;-- load n
%23 = load i32, i32* %4, align 4 ;-- load d
%24 = srem i32 %22, %23 ;-- n % d
%25 = icmp ne i32 %24, 0 ;-- (n % d) != 0
br i1 %25, label %second, label %notprime
 
second:
%26 = load i32, i32* %4, align 4 ;-- load d
%27 = add nsw i32 %26, 2 ;-- increment d by 2
store i32 %27, i32* %4, align 4 ;-- store d
%28 = load i32, i32* %3, align 4 ;-- load n
%29 = load i32, i32* %4, align 4 ;-- load d
%30 = srem i32 %28, %29 ;-- n % d
%31 = icmp ne i32 %30, 0 ;-- (n % d) != 0
br i1 %31, label %loop_end, label %notprime
 
loop_end:
%32 = load i32, i32* %4, align 4 ;-- load d
%33 = add nsw i32 %32, 4 ;-- increment d by 4
store i32 %33, i32* %4, align 4 ;-- store d
br label %loop
 
notprime:
store i1 false, i1* %2, align 1 ;-- store false in return value
br label %exit
 
prime:
store i1 true, i1* %2, align 1 ;-- store true in return value
br label %exit
 
exit:
%34 = load i1, i1* %2, align 1 ;-- load return value
ret i1 %34
}
 
; Function Attrs: noinline nounwind optnone uwtable
define i32 @count_prime_factors(i32) #0 {
%2 = alloca i32, align 4 ;-- allocate return value
%3 = alloca i32, align 4 ;-- allocate n
%4 = alloca i32, align 4 ;-- allocate count
%5 = alloca i32, align 4 ;-- allocate f
store i32 %0, i32* %3, align 4 ;-- store local copy of n
store i32 0, i32* %4, align 4 ;-- store zero in count
store i32 2, i32* %5, align 4 ;-- store 2 in f
%6 = load i32, i32* %3, align 4 ;-- load n
%7 = icmp eq i32 %6, 1 ;-- n == 1
br i1 %7, label %eq1, label %ne1
 
eq1:
store i32 0, i32* %2, align 4 ;-- store zero in return value
br label %exit
 
ne1:
%8 = load i32, i32* %3, align 4 ;-- load n
%9 = call zeroext i1 @is_prime(i32 %8) ;-- is n prime?
br i1 %9, label %prime, label %loop
 
prime:
store i32 1, i32* %2, align 4 ;-- store a in return value
br label %exit
 
loop:
%10 = load i32, i32* %3, align 4 ;-- load n
%11 = load i32, i32* %5, align 4 ;-- load f
%12 = srem i32 %10, %11 ;-- n % f
%13 = icmp ne i32 %12, 0 ;-- (n % f) != 0
br i1 %13, label %br2, label %br1
 
br1:
%14 = load i32, i32* %4, align 4 ;-- load count
%15 = add nsw i32 %14, 1 ;-- increment count
store i32 %15, i32* %4, align 4 ;-- store count
%16 = load i32, i32* %5, align 4 ;-- load f
%17 = load i32, i32* %3, align 4 ;-- load n
%18 = sdiv i32 %17, %16 ;-- n / f
store i32 %18, i32* %3, align 4 ;-- n = n / f
%19 = load i32, i32* %3, align 4 ;-- load n
%20 = icmp eq i32 %19, 1 ;-- n == 1
br i1 %20, label %br1_1, label %br1_2
 
br1_1:
%21 = load i32, i32* %4, align 4 ;-- load count
store i32 %21, i32* %2, align 4 ;-- store the count in the return value
br label %exit
 
br1_2:
%22 = load i32, i32* %3, align 4 ;-- load n
%23 = call zeroext i1 @is_prime(i32 %22) ;-- is n prime?
br i1 %23, label %br1_3, label %loop
 
br1_3:
%24 = load i32, i32* %3, align 4 ;-- load n
store i32 %24, i32* %5, align 4 ;-- f = n
br label %loop
 
br2:
%25 = load i32, i32* %5, align 4 ;-- load f
%26 = icmp sge i32 %25, 3 ;-- f >= 3
br i1 %26, label %br2_1, label %br3
 
br2_1:
%27 = load i32, i32* %5, align 4 ;-- load f
%28 = add nsw i32 %27, 2 ;-- increment f by 2
store i32 %28, i32* %5, align 4 ;-- store f
br label %loop
 
br3:
store i32 3, i32* %5, align 4 ;-- store 3 in f
br label %loop
 
exit:
%29 = load i32, i32* %2, align 4 ;-- load return value
ret i32 %29
}
 
; Function Attrs: noinline nounwind optnone uwtable
define i32 @main() #0 {
%1 = alloca i32, align 4 ;-- allocate i
%2 = alloca i32, align 4 ;-- allocate n
%3 = alloca i32, align 4 ;-- count
store i32 0, i32* %3, align 4 ;-- store zero in count
%4 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([52 x i8], [52 x i8]* @"ATTRACTIVE_STR", i32 0, i32 0), i32 120)
store i32 1, i32* %1, align 4 ;-- store 1 in i
br label %loop
 
loop:
%5 = load i32, i32* %1, align 4 ;-- load i
%6 = icmp sle i32 %5, 120 ;-- i <= 120
br i1 %6, label %loop_body, label %exit
 
loop_body:
%7 = load i32, i32* %1, align 4 ;-- load i
%8 = call i32 @count_prime_factors(i32 %7) ;-- count factors of i
store i32 %8, i32* %2, align 4 ;-- store factors in n
%9 = call zeroext i1 @is_prime(i32 %8) ;-- is n prime?
br i1 %9, label %prime_branch, label %loop_inc
 
prime_branch:
%10 = load i32, i32* %1, align 4 ;-- load i
%11 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @"FORMAT_NUMBER", i32 0, i32 0), i32 %10)
%12 = load i32, i32* %3, align 4 ;-- load count
%13 = add nsw i32 %12, 1 ;-- increment count
store i32 %13, i32* %3, align 4 ;-- store count
%14 = srem i32 %13, 20 ;-- count % 20
%15 = icmp ne i32 %14, 0 ;-- (count % 20) != 0
br i1 %15, label %loop_inc, label %row_end
 
row_end:
%16 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @"NEWLINE_STR", i32 0, i32 0))
br label %loop_inc
 
loop_inc:
%17 = load i32, i32* %1, align 4 ;-- load i
%18 = add nsw i32 %17, 1 ;-- increment i
store i32 %18, i32* %1, align 4 ;-- store i
br label %loop
 
exit:
%19 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @"NEWLINE_STR", i32 0, i32 0))
ret i32 0
}
 
attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Lua[edit]

-- Returns true if x is prime, and false otherwise
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
 
-- Compute the prime factors of n
function factors (n)
local facList, divisor, count = {}, 1
if n < 2 then return facList end
while not isPrime(n) do
while not isPrime(divisor) do divisor = divisor + 1 end
count = 0
while n % divisor == 0 do
n = n / divisor
table.insert(facList, divisor)
end
divisor = divisor + 1
if n == 1 then return facList end
end
table.insert(facList, n)
return facList
end
 
-- Main procedure
for i = 1, 120 do
if isPrime(#factors(i)) then io.write(i .. "\t") end
end
Output:
4       6       8       9       10      12      14      15      18      20      21      22      25      26      27
28      30      32      33      34      35      38      39      42      44      45      46      48      49      50
51      52      55      57      58      62      63      65      66      68      69      70      72      74      75
76      77      78      80      82      85      86      87      91      92      93      94      95      98      99
102     105     106     108     110     111     112     114     115     116     117     118     119     120

Maple[edit]

attractivenumbers := proc(n::posint)
local an, i;
an :=[]:
for i from 1 to n do
if isprime(NumberTheory:-NumberOfPrimeFactors(i)) then
an := [op(an), i]:
end if:
end do:
end proc:
attractivenumbers(120);
Output:
[4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120]

Nim[edit]

Translation of: C
import strformat
 
const MAX = 120
 
proc isPrime(n: int): bool =
var d = 5
if n < 2:
return false
if n mod 2 == 0:
return n == 2
if n mod 3 == 0:
return n == 3
while d * d <= n:
if n mod d == 0:
return false
inc d, 2
if n mod d == 0:
return false
inc d, 4
return true
 
proc countPrimeFactors(n_in: int): int =
var count = 0
var f = 2
var n = n_in
if n == 1:
return 0
if isPrime(n):
return 1
while true:
if n mod f == 0:
inc count
n = n div f
if n == 1:
return count
if isPrime(n):
f = n
elif (f >= 3):
inc f, 2
else:
f = 3
 
proc main() =
var n, count: int = 0
echo fmt"The attractive numbers up to and including {MAX} are:"
for i in 1..MAX:
n = countPrimeFactors(i)
if isPrime(n):
write(stdout, fmt"{i:4d}")
inc count
if count mod 20 == 0:
write(stdout, "\n")
write(stdout, "\n")
 
main()
 
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Perl[edit]

Library: ntheory
use ntheory <is_prime factor>;
 
is_prime +factor $_ and print "$_ " for 1..120;
Output:
4 6 8 9 10 12 14 15 18 20 21 22 25 26 27 28 30 32 33 34 35 38 39 42 44 45 46 48 49 50 51 52 55 57 58 62 63 65 66 68 69 70 72 74 75 76 77 78 80 82 85 86 87 91 92 93 94 95 98 99 102 105 106 108 110 111 112 114 115 116 117 118 119 120

Perl 6[edit]

Works with: Rakudo version 2019.03

This algorithm is concise but not really well suited to finding large quantities of consecutive attractive numbers. It works, but isn't especially speedy. More than a hundred thousand or so gets tedious. There are other, much faster (though more verbose) algorithms that could be used. This algorithm is well suited to finding arbitrary attractive numbers though.

use Lingua::EN::Numbers;
use ntheory:from<Perl5> <factor is_prime>;
 
sub display ($n,$m) { ($n..$m).grep: (~*).&factor.elems.&is_prime }
 
sub count ($n,$m) { +($n..$m).grep: (~*).&factor.elems.&is_prime }
 
# The Task
put "Attractive numbers from 1 to 120:\n" ~
display(1, 120)».fmt("%3d").rotor(20, :partial).join: "\n";
 
# Robusto!
for 1, 1000, 1, 10000, 1, 100000, 2**73 + 1, 2**73 + 100 -> $a, $b {
put "\nCount of attractive numbers from {comma $a} to {comma $b}:\n" ~
comma count $a, $b
}
Output:
Attractive numbers from 1 to 120:
  4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
 35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
 69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
102 105 106 108 110 111 112 114 115 116 117 118 119 120

Count of attractive numbers from 1 to 1,000:
636

Count of attractive numbers from 1 to 10,000:
6,396

Count of attractive numbers from 1 to 100,000:
63,255

Count of attractive numbers from 9,444,732,965,739,290,427,393 to 9,444,732,965,739,290,427,492:
58

Phix[edit]

function attractive(integer lim)
sequence s = {}
for i=1 to lim do
integer n = length(prime_factors(i,true))
if is_prime(n) then s &= i end if
end for
return s
end function
sequence s = attractive(120)
printf(1,"There are %d attractive numbers up to and including %d:\n",{length(s),120})
pp(s,{pp_IntCh,false})
for i=3 to 5 do
integer p = power(10,i)
printf(1,"There are %,d attractive numbers up to %,d\n",{length(attractive(p)),p})
end for
Output:
There are 74 attractive numbers up to and including 120:
{4,6,8,9,10,12,14,15,18,20,21,22,25,26,27,28,30,32,33,34,35,38,39,42,44,45,
 46,48,49,50,51,52,55,57,58,62,63,65,66,68,69,70,72,74,75,76,77,78,80,82,85,
 86,87,91,92,93,94,95,98,99,102,105,106,108,110,111,112,114,115,116,117,118,
 119,120}
There are 636 attractive numbers up to 1,000
There are 6,396 attractive numbers up to 10,000
There are 63,255 attractive numbers up to 100,000

Python[edit]

Procedural[edit]

Works with: Python version 2.7.12
from sympy import sieve # library for primes
 
def get_pfct(n):
i = 2; factors = []
while i * i <= n:
if n % i:
i += 1
else:
n //= i
factors.append(i)
if n > 1:
factors.append(n)
return len(factors)
 
sieve.extend(110) # first 110 primes...
primes=sieve._list
 
pool=[]
 
for each in xrange(0,121):
pool.append(get_pfct(each))
 
for i,each in enumerate(pool):
if each in primes:
print i,
Output:
4,6,8,9,10,12,14,15,18,20,21,22,25,26,27,28,30,32,33,34,35,38,39,42,44,45,46, 48,49,50,51,52,55,57,58,62,63,65,66,68,69,70,72,74,75,76,77,78,80,82,85,86,87, 91,92,93,94,95,98,99,102,105,106,108,110,111,112,114,115,116,117,118,119,120

Functional[edit]

Without importing a primes library – at this scale a light and visible implementation is more than enough, and provides more material for comparison.

Works with: Python version 3.7
'''Attractive numbers'''
 
from itertools import chain, count, takewhile
from functools import reduce
 
 
# attractiveNumbers :: () -> [Int]
def attractiveNumbers():
'''A non-finite stream of attractive numbers.
(OEIS A063989)
'''

return filter(
compose(
isPrime,
len,
primeDecomposition
),
count(1)
)
 
 
# TEST ----------------------------------------------------
def main():
'''Attractive numbers drawn from the range [1..120]'''
for row in chunksOf(15)(list(
takewhile(
lambda x: 120 >= x,
attractiveNumbers()
)
)):
print(' '.join(map(
compose(justifyRight(3)(' '), str),
row
)))
 
 
# GENERAL FUNCTIONS ---------------------------------------
 
# chunksOf :: Int -> [a] -> [[a]]
def chunksOf(n):
'''A series of lists of length n, subdividing the
contents of xs. Where the length of xs is not evenly
divible, the final list will be shorter than n.
'''

return lambda xs: reduce(
lambda a, i: a + [xs[i:n + i]],
range(0, len(xs), n), []
) if 0 < n else []
 
 
# 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
)
 
 
# We only need light implementations
# of prime functions here:
 
# primeDecomposition :: Int -> [Int]
def primeDecomposition(n):
'''List of integers representing the
prime decomposition of n.
'''

def go(n, p):
return [p] + go(n // p, p) if (
0 == n % p
) else []
return list(chain.from_iterable(map(
lambda p: go(n, p) if isPrime(p) else [],
range(2, 1 + n)
)))
 
 
# 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
 
return not any(map(
lambda x: 0 == n % x or 0 == n % (2 + x),
range(5, 1 + int(n ** 0.5), 6)
))
 
 
# justifyRight :: Int -> Char -> String -> String
def justifyRight(n):
'''A string padded at left to length n,
using the padding character c.
'''

return lambda c: lambda s: s.rjust(n, c)
 
 
# MAIN ---
if __name__ == '__main__':
main()
Output:
  4   6   8   9  10  12  14  15  18  20  21  22  25  26  27
 28  30  32  33  34  35  38  39  42  44  45  46  48  49  50
 51  52  55  57  58  62  63  65  66  68  69  70  72  74  75
 76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
102 105 106 108 110 111 112 114 115 116 117 118 119 120

Racket[edit]

#lang racket
(require math/number-theory)
(define attractive? (compose1 prime? prime-omega))
(filter attractive? (range 1 121))
Output:
(4 6 8 9 10 12 14 15 18 20 21 22 25 26 27 28 30 32 33 34 35 38 39 42 44 45 46 48 49 50 51 52 55 57 58 62 63 65 66 68 69 70 72 74 75 76 77 78 80 82 85 86 87 91 92 93 94 95 98 99 102 105 106 108 110 111 112 114 115 116 117 118 119 120)

REXX[edit]

Programming notes: The use of a table that contains some low primes is one fast method to test for primality of the
various prime factors.

The   cFact   (count factors)   function   is optimized way beyond what this task requires,   and it can be optimized
further by expanding the     do whiles     clauses   (lines   3──►6   in the   cFact   function).

/*REXX program finds and shows lists (or counts) attractive numbers up to a specified N.*/
parse arg N . /*get optional argument from the C.L. */
if N=='' | N=="," then N= 120 /*Not specified? Then use the default.*/
cnt= N<0 /*semaphore used to control the output.*/
N= abs(N) /*ensure that N is a positive number.*/
call genP 100 /*gen 100 primes (high= 541); overkill.*/
sw= linesize() - 1 /*SW: is the usable screen width. */
if \cnt then say 'attractive numbers up to and including ' N " are:"
#= 0 /*number of attractive #'s (so far). */
$= /*a list of attractive numbers (so far)*/
do j=1 for N; if @.j then iterate /*Is it a prime? Then skip the number.*/
a= cFact(j) /*call cFact to count the factors in J.*/
if \@.a then iterate /*if # of factors not prime, then skip.*/
#= # + 1 /*add the index and number of factors.*/
if cnt then iterate /*if not displaying numbers, skip list.*/
_= $ j /*append a number to $ list.*/
if length(_)>sw then do; say strip($); $= j; end /*display a line of numbers.*/
else $= _ /*append the latest number. */
end /*j*/
 
if $\=='' & \cnt then say strip($) /*display any residual numbers in list.*/
say; say # ' attractive numbers found up to and including ' N
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
cFact: procedure; parse arg z 1 oz; if z<2 then return z /*if Z too small, return Z.*/
#= 0 /*#: is the number of factors (so far)*/
do while z//2==0; #= #+1; z= z%2; end /*maybe add the factor of two. */
do while z//3==0; #= #+1; z= z%3; end /* " " " " " three.*/
do while z//5==0; #= #+1; z= z%5; end /* " " " " " five. */
do while z//7==0; #= #+1; z= z%7; end /* " " " " " seven.*/
/* [↑] reduce Z by some low primes. */
do k=11 by 6 while k<=z /*insure that K isn't divisible by 3.*/
parse var k '' -1 _ /*obtain the last decimal digit of K. */
if _\==5 then do while z//k==0; #= #+1; z= z%k; end /*maybe reduce Z.*/
if _ ==3 then iterate /*Next number ÷ by 5? Skip. ____ */
if k*k>oz then leave /*are we greater than the √ OZ  ? */
y= k + 2 /*get next divisor, hopefully a prime.*/
do while z//y==0; #= #+1; z= z%y; end /*maybe reduce Z.*/
end /*k*/
if z\==1 then return # + 1 /*if residual isn't unity, then add it.*/
return # /*return the number of factors in OZ. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
genP: procedure expose @.; parse arg n; @.=0; @.2= 1; @.3= 1; p= 2
do j=3 by 2 until p==n; do k=3 by 2 until k*k>j; if j//k==0 then iterate j
end /*k*/; @.j = 1; p= p + 1
end /*j*/; return /* [↑] generate N primes. */

This REXX program makes use of   LINESIZE   REXX program (or BIF) which is used to determine the screen width (or linesize) of the terminal (console).
Some REXXes don't have this BIF.   It is used here to automatically/idiomatically limit the width of the output list.

The   LINESIZE.REX   REXX program is included here   ───►   LINESIZE.REX.


output   when using the default input:
attractive numbers up to and including  120  are:
4 6 8 9 10 12 14 15 18 20 21 22 25 26 27 28 30 32 33 34 35 38 39 42 44 45 46 48 49 50 51 52 55 57 58 62 63 65 66 68 69 70 72 74
75 76 77 78 80 82 85 86 87 91 92 93 94 95 98 99 102 105 106 108 110 111 112 114 115 116 117 118 119 120

74  attractive numbers found up to and including  120
output   when using the input of:     -10000
6396  attractive numbers found up to and including  10000

Ring[edit]

 
# Project: Attractive Numbers
 
decomp = []
nump = 0
see "Attractive Numbers up to 120:" + nl
while nump < 120
decomp = []
nump = nump + 1
for i = 1 to nump
if isPrime(i) and nump%i = 0
add(decomp,i)
dec = nump/i
while dec%i = 0
add(decomp,i)
dec = dec/i
end
ok
next
if isPrime(len(decomp))
see string(nump) + " = ["
for n = 1 to len(decomp)
if n < len(decomp)
see string(decomp[n]) + "*"
else
see string(decomp[n]) + "] - " + len(decomp) + " is prime" + nl
ok
next
ok
end
 
 
func isPrime(num)
if (num <= 1) return 0 ok
if (num % 2 = 0) and num != 2 return 0 ok
for i = 3 to floor(num / 2) -1 step 2
if (num % i = 0) return 0 ok
next
return 1
 
Output:
Attractive Numbers up to 120:
4 = [2*2] - 2 is prime
6 = [2*3] - 2 is prime
8 = [2*2*2] - 3 is prime
9 = [3*3] - 2 is prime
10 = [2*5] - 2 is prime
12 = [2*2*3] - 3 is prime
14 = [2*7] - 2 is prime
15 = [3*5] - 2 is prime
18 = [2*3*3] - 3 is prime
20 = [2*2*5] - 3 is prime
...
...
...
102 = [2*3*17] - 3 is prime
105 = [3*5*7] - 3 is prime
106 = [2*53] - 2 is prime
108 = [2*2*3*3*3] - 5 is prime
110 = [2*5*11] - 3 is prime
111 = [3*37] - 2 is prime
112 = [2*2*2*2*7] - 5 is prime
114 = [2*3*19] - 3 is prime
115 = [5*23] - 2 is prime
116 = [2*2*29] - 3 is prime
117 = [3*3*13] - 3 is prime
118 = [2*59] - 2 is prime
119 = [7*17] - 2 is prime
120 = [2*2*2*3*5] - 5 is prime

Ruby[edit]

require "prime"
 
p (1..120).select{|n| n.prime_division.sum(&:last).prime? }
 
Output:
[4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120]

Rust[edit]

Uses primal

use primal::Primes;
 
const MAX: u64 = 120;
 
/// Returns an Option with a tuple => Ok((smaller prime factor, num divided by that prime factor))
/// If num is a prime number itself, returns None
fn extract_prime_factor(num: u64) -> Option<(u64, u64)> {
let mut i = 0;
if primal::is_prime(num) {
None
} else {
loop {
let prime = Primes::all().nth(i).unwrap() as u64;
if num % prime == 0 {
return Some((prime, num / prime));
} else {
i += 1;
}
}
}
}
 
/// Returns a vector containing all the prime factors of num
fn factorize(num: u64) -> Vec<u64> {
let mut factorized = Vec::new();
let mut rest = num;
while let Some((prime, factorizable_rest)) = extract_prime_factor(rest) {
factorized.push(prime);
rest = factorizable_rest;
}
factorized.push(rest);
factorized
}
 
fn main() {
let mut output: Vec<u64> = Vec::new();
for num in 4 ..= MAX {
if primal::is_prime(factorize(num).len() as u64) {
output.push(num);
}
}
println!("The attractive numbers up to and including 120 are\n{:?}", output);
}
Output:
The attractive numbers up to and including 120 are
[4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120]

Scala[edit]

Output:
Best seen in running your browser either by ScalaFiddle (ES aka JavaScript, non JVM) or Scastie (remote JVM).
object AttractiveNumbers extends App {
private val max = 120
private var count = 0
 
private def nFactors(n: Int): Int = {
@scala.annotation.tailrec
def factors(x: Int, f: Int, acc: Int): Int =
if (f * f > x) acc + 1
else
x % f match {
case 0 => factors(x / f, f, acc + 1)
case _ => factors(x, f + 1, acc)
}
 
factors(n, 2, 0)
}
 
private def ls: Seq[String] =
for (i <- 4 to max;
n = nFactors(i)
if n >= 2 && nFactors(n) == 1 // isPrime(n)
) yield f"$i%4d($n)"
 
println(f"The attractive numbers up to and including $max%d are: [number(factors)]\n")
ls.zipWithIndex
.groupBy { case (_, index) => index / 20 }
.foreach { case (_, row) => println(row.map(_._1).mkString) }
}

Sidef[edit]

func is_attractive(n) {
n.bigomega.is_prime
}
 
1..120 -> grep(is_attractive).say
Output:
[4, 6, 8, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 55, 57, 58, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 102, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120]

Visual Basic .NET[edit]

Translation of: D
Module Module1
Const MAX = 120
 
Function IsPrime(n As Integer) As Boolean
If n < 2 Then Return False
If n Mod 2 = 0 Then Return n = 2
If n Mod 3 = 0 Then Return n = 3
Dim d = 5
While d * d <= n
If n Mod d = 0 Then Return False
d += 2
If n Mod d = 0 Then Return False
d += 4
End While
Return True
End Function
 
Function PrimefactorCount(n As Integer) As Integer
If n = 1 Then Return 0
If IsPrime(n) Then Return 1
Dim count = 0
Dim f = 2
While True
If n Mod f = 0 Then
count += 1
n /= f
If n = 1 Then Return count
If IsPrime(n) Then f = n
ElseIf f >= 3 Then
f += 2
Else
f = 3
End If
End While
Throw New Exception("Unexpected")
End Function
 
Sub Main()
Console.WriteLine("The attractive numbers up to and including {0} are:", MAX)
Dim i = 1
Dim count = 0
While i <= MAX
Dim n = PrimefactorCount(i)
If IsPrime(n) Then
Console.Write("{0,4}", i)
count += 1
If count Mod 20 = 0 Then
Console.WriteLine()
End If
End If
i += 1
End While
Console.WriteLine()
End Sub
 
End Module
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120

zkl[edit]

Using GMP (GNU Multiple Precision Arithmetic Library, probabilistic primes) because it is easy and fast to test for primeness.

var [const] BI=Import("zklBigNum");  // libGMP
fcn attractiveNumber(n){ BI(primeFactors(n).len()).probablyPrime() }
 
println("The attractive numbers up to and including 120 are:");
[1..120].filter(attractiveNumber)
.apply("%4d".fmt).pump(Void,T(Void.Read,19,False),"println");

Using Prime decomposition#zkl

fcn primeFactors(n){  // Return a list of factors of n
acc:=fcn(n,k,acc,maxD){ // k is 2,3,5,7,9,... not optimum
if(n==1 or k>maxD) acc.close();
else{
q,r:=n.divr(k); // divr-->(quotient,remainder)
if(r==0) return(self.fcn(q,k,acc.write(k),q.toFloat().sqrt()));
return(self.fcn(n,k+1+k.isOdd,acc,maxD))
}
}(n,2,Sink(List),n.toFloat().sqrt());
m:=acc.reduce('*,1); // mulitply factors
if(n!=m) acc.append(n/m); // opps, missed last factor
else acc;
}
Output:
The attractive numbers up to and including 120 are:
   4   6   8   9  10  12  14  15  18  20  21  22  25  26  27  28  30  32  33  34
  35  38  39  42  44  45  46  48  49  50  51  52  55  57  58  62  63  65  66  68
  69  70  72  74  75  76  77  78  80  82  85  86  87  91  92  93  94  95  98  99
 102 105 106 108 110 111 112 114 115 116 117 118 119 120