Math::NumSeq::PolignacObstinate -- odd integers not prime+2^k
use Math::NumSeq::PolignacObstinate; my $seq = Math::NumSeq::PolignacObstinate->new; my ($i, $value) = $seq->next;
This sequence is integers which cannot be represented as prime+2^k for an integer k. These are counter-examples to a conjecture by Prince de Polignac that every odd integer occurs as prime+2^k (and are called "obstinate" numbers by Andy Edwards).
1, 127, 149, 251, 331, 337, ...
For example 149 is obstinate because it cannot be written as prime+2^k. Working backwards, it can be seen that none of 149-1, 149-2, 149-4, 149-8, ... 149-128 are primes.
A theorem by Erdos gives infinitely many such obstinate integers (in an arithmetic progression).
The value 3 is not in the sequence because it can be written prime+2^k, for prime=2 and k=0.
See "FUNCTIONS" in Math::NumSeq for behaviour common to all sequence classes.
$seq = Math::NumSeq::PolignacObstinate->new ()
Create and return a new sequence object.
$bool = $seq->pred($value)
Return true if
$valueis obstinate, ie. that there's no
$k >= 0for which
$value - 2**$kis a prime.
This check requires prime testing up to
$valueand in the current code a hard limit of 2**32 is placed on the
$valueto be checked, in the interests of not going into a near-infinite loop.
Clifford Pickover, "The Grand Internet Obstinate Number Search"
Copyright 2010, 2011, 2012, 2013, 2014 Kevin Ryde
Math-NumSeq is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
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