Neighbour primes: Difference between revisions

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=={{header|ALGOL W}}==

<~~lang~~ algolw>begin % find some primes where ( p*q ) + 2 is also a prime ( where p and q are adjacent primes ) %

<syntaxhighlight lang="algolw">begin % find some primes where ( p*q ) + 2 is also a prime ( where p and q are adjacent primes ) %

% sets p( 1 :: n ) to a sieve of primes up to n %

procedure sieve ( logical array p( * ) ; integer value n ) ;

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write( i_w := 1, s_w := 0, "Found ", pCount, " neighbour primes up to 500" )

end

end.</~~lang~~>

end.</syntaxhighlight>

<pre>

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=={{header|AppleScript}}==

<~~lang~~ applescript>on isPrime(n)

<syntaxhighlight lang="applescript">on isPrime(n)

if (n < 6) then return ((n > 1) and (n is not 4))

if ((n mod 2 = 0) or (n mod 3 = 0) or (n mod 5 = 0)) then return false

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end neighbourPrimes

neighbourPrimes(499)</~~lang~~>

neighbourPrimes(499)</syntaxhighlight>

<~~lang~~ applescript>{3, 5, 7, 13, 19, 67, 149, 179, 229, 239, 241, 269, 277, 307, 313, 397, 401, 419, 439, 487}</~~lang~~>

=={{header|Arturo}}==

<~~lang~~ rebol>primesUpTo500: select 1..500 => prime?

<syntaxhighlight lang="rebol">primesUpTo500: select 1..500 => prime?

print [pad "p" 5 pad "q" 4 pad "p*q+2" 7]

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]

i: i + 1

]</~~lang~~>

]</syntaxhighlight>

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=={{header|AWK}}==

# syntax: GAWK -f NEIGHBOUR_PRIMES.AWK

BEGIN {

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return(1)

}

</syntaxhighlight>

</lang>

<pre>

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=={{header|BASIC}}==

==={{header|BASIC256}}===

<~~lang~~ ~~BASIC256~~>function isPrime(v)

<syntaxhighlight lang="basic256">function isPrime(v)

if v < 2 then return False

if v mod 2 = 0 then return v = 2

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print p; chr(9); q; chr(9); 2+p*q

next p

end</~~lang~~>

end</syntaxhighlight>

==={{header|PureBasic}}===

<~~lang~~ ~~PureBasic~~>Procedure isPrime(v.i)

<syntaxhighlight lang="purebasic">Procedure isPrime(v.i)

If v <= 1 : ProcedureReturn #False

ElseIf v < 4 : ProcedureReturn #True

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Next p

PrintN(#CRLF$ + "--- terminado, pulsa RETURN---"): Input()

CloseConsole()</~~lang~~>

CloseConsole()</syntaxhighlight>

==={{header|Yabasic}}===

<~~lang~~ yabasic>sub isPrime(v)

<syntaxhighlight lang="yabasic">sub isPrime(v)

if v < 2 then return False : fi

if mod(v, 2) = 0 then return v = 2 : fi

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print p, chr$(9), q, chr$(9), 2+p*q

next p

end</~~lang~~>

end</syntaxhighlight>

=={{header|C#|CSharp}}==

How about some other offsets besides <code>+ 2</code> ?

<~~lang~~ fsharp>using System; using System.Collections.Generic;

<syntaxhighlight lang="fsharp">using System; using System.Collections.Generic;

using System.Linq; using static System.Console; using System.Collections;

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if (!flags[j]) { yield return j;

for (int k = sq, i=j<<1; k<=lim; k += i) flags[k] = true; }

for (; j <= lim; j += 2) if (!flags[j]) yield return j; } }</~~lang~~>

for (; j <= lim; j += 2) if (!flags[j]) yield return j; } }</syntaxhighlight>

<pre>Multiply two consecutive prime numbers, add an even number, see if the result is a prime number (up to a limit).

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=={{header|F_Sharp|F#}}==

This task uses [http://www.rosettacode.org/wiki/Extensible_prime_generator#The_functions Extensible Prime Generator (F#)]

<~~lang~~ fsharp>

// Nigel Galloway. April 13th., 2021

primes32()|>Seq.pairwise|>Seq.takeWhile(fun(n,_)->n<500)|>Seq.filter(fun(n,g)->isPrime(n*g+2))|>Seq.iter(fun(n,g)->printfn "%d*%d=%d" n g (n*g+2))

</syntaxhighlight>

</lang>

<pre>

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=={{header|Factor}}==

<~~lang~~ factor>USING: formatting io kernel math math.primes ;

<syntaxhighlight lang="factor">USING: formatting io kernel math math.primes ;

"p q p*q+2" print

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[ 3dup "%-4d %-4d %-6d\n" printf ] when

drop nip dup next-prime

] while 2drop</~~lang~~>

] while 2drop</syntaxhighlight>

<pre>

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=={{header|Fermat}}==

<~~lang~~ fermat>for i = 1 to 95 do if Isprime(2+Prime(i)*Prime(i+1)) then !!Prime(i) fi od</~~lang~~>

<syntaxhighlight lang="fermat">for i = 1 to 95 do if Isprime(2+Prime(i)*Prime(i+1)) then !!Prime(i) fi od</syntaxhighlight>

=={{header|FreeBASIC}}==

<~~lang~~ freebasic>#include "isprime.bas"

<syntaxhighlight lang="freebasic">#include "isprime.bas"

dim as uinteger q

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if not isprime( 2 + p*q ) then continue for

print p,q,2+p*q

next p</~~lang~~>

next p</syntaxhighlight>

<pre>

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<~~lang~~ go>package main

<syntaxhighlight lang="go">package main

import (

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rcu.PrintTable(nprimes, 10, 3, false)

fmt.Println("\nFound", len(nprimes), "such primes.")

}</~~lang~~>

}</syntaxhighlight>

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This entry uses `is_prime` as defined at [[Erd%C5%91s-primes#jq]].

<~~lang~~ jq>def next_prime:

<syntaxhighlight lang="jq">def next_prime:

if . == 2 then 3

else first(range(.+2; infinite; 2) | select(is_prime))

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| .p = $np )

| select(.emit).emit

</syntaxhighlight>

</lang>

<pre>

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=={{header|Julia}}==

<~~lang~~ julia>using Primes

<syntaxhighlight lang="julia">using Primes

isneiprime(known) = isprime(known) && isprime(known * nextprime(known + 1) + 2)

println(filter(isneiprime, primes(500)))

</~~lang~~>{{out}}<pre>[3, 5, 7, 13, 19, 67, 149, 179, 229, 239, 241, 269, 277, 307, 313, 397, 401, 419, 439, 487]</pre>

</syntaxhighlight>{{out}}<pre>[3, 5, 7, 13, 19, 67, 149, 179, 229, 239, 241, 269, 277, 307, 313, 397, 401, 419, 439, 487]</pre>

=={{header|Ksh}}==

<~~lang~~ ksh>

#!/bin/ksh

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np=$(_neighbourprime ${i} parr)

(( np > 0 )) && printf "%3d %3d %6d\n" ${parr[i]} ${parr[i+1]} ${np}

done</~~lang~~>

done</syntaxhighlight>

{{out}}<pre>

p q p*q+2

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=={{header|Mathematica}}/{{header|Wolfram Language}}==

<~~lang~~ ~~Mathematica~~>p = Prime@Range@PrimePi[499];

<syntaxhighlight lang="mathematica">p = Prime@Range@PrimePi[499];

Select[p, PrimeQ[# NextPrime[#] + 2] &]</~~lang~~>

Select[p, PrimeQ[# NextPrime[#] + 2] &]</syntaxhighlight>

=={{header|Nim}}==

<~~lang~~ ~~Nim~~>import strformat, sugar

<syntaxhighlight lang="nim">import strformat, sugar

const

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if (p * q + 2).isPrime:

echo &"{p:3} {q:3} {p*q+2:6}"

p = q</~~lang~~>

p = q</syntaxhighlight>

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=={{header|PARI/GP}}==

Cheats a little in the sense that it requires knowing the 95th prime is 499 beforehand.

<~~lang~~ parigp>for(i=1, 95, if(isprime(2+prime(i)*prime(i+1)),print(prime(i))))</~~lang~~>

<syntaxhighlight lang="parigp">for(i=1, 95, if(isprime(2+prime(i)*prime(i+1)),print(prime(i))))</syntaxhighlight>

=={{header|Perl}}==

<~~lang~~ perl>use strict;

<syntaxhighlight lang="perl">use strict;

use warnings;

use ntheory <next_prime is_prime>;

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printf "%3d%5d%8d\n", $p, $q, $p*$q+2 if is_prime $p*$q+2;

$p = $q;

} until $p >= 500;</~~lang~~>

} until $p >= 500;</syntaxhighlight>

<pre> 3 5 17

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=={{header|Phix}}==

function np(integer p) return is_prime(get_prime(p)*get_prime(p+1)+2) end function

constant N = length(get_primes_le(500))

sequence res = apply(apply(filter(tagset(N),np),get_prime),sprint)

printf(1,"Found %d such primes: %s\n",{length(res),join(shorten(res,"",5),", ")})

<pre>

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=={{header|Python}}==

<~~lang~~ python>#!/usr/bin/python

<syntaxhighlight lang="python">#!/usr/bin/python

def isPrime(n):

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if not isPrime(2 + p*q):

continue

print(p, "\t", q, "\t", 2+p*q)</~~lang~~>

print(p, "\t", q, "\t", 2+p*q)</syntaxhighlight>

<pre>p q pq+2

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=={{header|Raku}}==

<lang ~~perl6~~>my @primes = grep &is-prime, ^Inf;

<syntaxhighlight lang="raku" line>my @primes = grep &is-prime, ^Inf;

my $last_p = @primes.first: :k, * >= 500;

my $last_q = $last_p + 1;

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.grep( *.[2].is-prime );

say .fmt('%6d') for @cousins;</~~lang~~>

say .fmt('%6d') for @cousins;</syntaxhighlight>

<pre>

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=={{header|REXX}}==

'''Neighbor''' primes can also be spelled '''neighbour''' primes.

<~~lang~~ rexx>/*REXX program finds neighbor primes: P, Q, P*Q+2 are primes, and P < some specified N.*/

<syntaxhighlight lang="rexx">/*REXX program finds neighbor primes: P, Q, P*Q+2 are primes, and P < some specified N.*/

parse arg hi cols . /*obtain optional argument from the CL.*/

if hi=='' | hi=="," then hi= 500 /*Not specified? Then use the default.*/

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end /*k*/ /* [↑] only process numbers ≤ √ J */

#= #+1; @.#= j; s.#= j*j; !.j= 1 /*bump # of Ps; assign next P; P²; P# */

end /*j*/; return</~~lang~~>

end /*j*/; return</syntaxhighlight>

<pre>

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=={{header|Ring}}==

<~~lang~~ ring>

load "stdlib.ring"

see "working..." + nl

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see "Found " + row + " neighbour primes" + nl

see "done..." + nl

</syntaxhighlight>

</lang>

<pre>

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=={{header|Sidef}}==

<~~lang~~ ruby>500.primes.grep {|p| p * p.next_prime + 2 -> is_prime }.say</~~lang~~>

<syntaxhighlight lang="ruby">500.primes.grep {|p| p * p.next_prime + 2 -> is_prime }.say</syntaxhighlight>

<pre>

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<~~lang~~ ecmascript>import "/math" for Int

<syntaxhighlight lang="ecmascript">import "/math" for Int

import "/seq" for Lst

import "/fmt" for Fmt

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}

for (chunk in Lst.chunks(nprimes, 10)) Fmt.print("$3d", chunk)

System.print("\nFound %(nprimes.count) such primes.")</~~lang~~>

System.print("\nFound %(nprimes.count) such primes.")</syntaxhighlight>

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=={{header|XPL0}}==

<~~lang~~ ~~XPL0~~>func IsPrime(N); \Return 'true' if N is a prime number

<syntaxhighlight lang="xpl0">func IsPrime(N); \Return 'true' if N is a prime number

int N, I;

[if N <= 1 then return false;

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Text(0, " neighbour primes found below 500.

");

]</~~lang~~>

]</syntaxhighlight>