De Polignac numbers: Difference between revisions

=={{header|Euler}}==

Basic task only.<br/>

Based on the Algol W sample, but as 3 is clearly not a de Polignac number, only considers odd primes.

'''begin''' '''new''' isOddPrime;

isOddPrime

&lt;- ` '''formal''' n;

'''if''' n '''mod''' 2 = 0

'''then''' '''false'''

'''else''' '''begin'''

'''new''' prime; '''new''' f; '''new''' f2; '''new''' toNext; '''label''' primeLoop;

prime &lt;- '''true''';

f &lt;- 3;

f2 &lt;- 9;

toNext &lt;- 16;

primeLoop: '''if''' f2 &lt;= n '''and''' prime '''then''' '''begin'''

prime &lt;- n '''mod''' f &lt;&gt; 0;

f &lt;- f + 2;

f2 &lt;- toNext;

toNext &lt;- toNext + 8;

'''goto''' primeLoop '''end''' '''else''' 0;

prime

'''end'''

&apos;;

'''begin''' '''new''' n; '''new''' count; '''label''' forI;

count &lt;- 0;

n &lt;- -1;

forI: '''if''' '''begin''' n &lt;- n + 2; count &lt; 50 '''end''' '''then''' '''begin'''

'''new''' found; '''new''' p; '''new''' powerOf2; '''label''' p2Loop;

found &lt;- '''false''';

powerOf2 &lt;- 1;

p2Loop: '''if''' '''not''' found '''and''' n &gt; powerOf2 '''then''' '''begin'''

found &lt;- isOddPrime( n - powerOf2 );

powerOf2 &lt;- powerOf2 * 2;

'''goto''' p2Loop '''end''' '''else''' 0;

'''if''' '''not''' found '''then''' '''begin'''

count &lt;- count + 1;

'''out''' n

'''end''' '''else''' 0;

'''goto''' forI '''end''' '''else''' 0

'''end'''

'''end''' $

{{out}}

<pre>

NUMBER 1

NUMBER 127

NUMBER 149

...

NUMBER 2171

NUMBER 2203

NUMBER 2213

</pre>