Prime numbers whose neighboring pairs are tetraprimes: Difference between revisions
Prime numbers whose neighboring pairs are tetraprimes (view source)
Revision as of 14:51, 24 June 2023
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{{works with|ALGOL 68G|Any - tested with release 2.8.3.win32}}
{{libheader|ALGOL 68-rows}}
Constructs a table of prime factors without using division/modulo
To run this wityth Algol 68G, you will need to specify a large heap size, with e.g.: <code>-heap 256M</code> on the command line.
<syntaxhighlight lang="algol68">
BEGIN # find primes whose neighbouring pairs are tetraprimes - i.e. have 4 #
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BEGIN
# array of prime gaps, used to find the median gap #
# should be large enough for the
INT t count := 0, f7 count := 0;
INT prev prime := 0;
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# task #
show tetraprime neighbours( 100 000, TRUE );
show tetraprime neighbours( 1 000 000, FALSE );
show tetraprime neighbours( 10 000 000, FALSE )
END
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Found 866 such primes of which 492 have 7 as a factor of one of the pair
gaps between the primes: min: 4, average: 1146, median: 832, max: 10284
Primes below 10000000 preceded by a tetraprime pair:
Found 10815 such primes of which 5176 have 7 as a factor of one of the pair
gaps between the primes: min: 4, average: 924, median: 648, max: 9352
Primes below 10000000 followed by a tetraprime pair:
Found 10551 such primes of which 5069 have 7 as a factor of one of the pair
gaps between the primes: min: 4, average: 947, median: 660, max: 10284
</pre>
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