Math::NumSeq::SophieGermainPrimes -- Sophie Germain primes p and 2*p+1 prime
use Math::NumSeq::SophieGermainPrimes; my $seq = Math::NumSeq::SophieGermainPrimes->new; my ($i, $value) = $seq->next;
The primes P for which 2*P+1 is also prime,
2, 3, 5, 11, 23, 29, 41, 53, 83, 89, 113, 131, 173, 179, ... starting i=1
See "FUNCTIONS" in Math::NumSeq for behaviour common to all sequence classes.
$seq = Math::NumSeq::SophieGermainPrimes->new ()
Create and return a new sequence object.
$bool = $seq->pred($value)
Return true if
$value is a Sophie Germain prime, meaning both
2*$value+1 are prime.
$i = $seq->value_to_i_estimate($value)
Return an estimate of the i corresponding to
Currently this is the same as the TwinPrimes estimate. Is it a conjecture by Hardy and Littlewood that the two are asymptotically the same? In any case the result is roughly a factor 0.9 too small for the small to medium size integers this module might calculate. (See Math::NumSeq::TwinPrimes.)
next() is implemented by a
Math::NumSeq::Primes sequence filtered for primes where 2P+1 is a prime too. Dana Jacobsen noticed this is faster than running a second Primes iterator for primes 2P+1. This is since for a prime P often 2P+1 has a small factor such as 3, 5 or 11. A factor 3 occurs for any P=6k+1 since in that case 2P+1 is a multiple of 3. What else can be said about the density or chance of a small factor?
Copyright 2010, 2011, 2012, 2013, 2014 Kevin Ryde
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