Math::NumSeq::PrimeFactorCount -- how many prime factors
use Math::NumSeq::PrimeFactorCount; my $seq = Math::NumSeq::PrimeFactorCount->new; my ($i, $value) = $seq->next;
The sequence of how many prime factors in i, being
0, 1, 1, 2, 1, 2, ...
The sequence starts from i=1 and 1 is taken to have no prime factors. Then i=2 and i=3 are themselves primes, so 1 prime factor. Then i=4 is 2*2 which is 2 prime factors.
multiplicity => "distinct" option can control whether repeats of a prime factors are counted, or only distinct primes. For example with "distinct" i=4=2*2 is just 1 prime factor.
See "FUNCTIONS" in Math::NumSeq for behaviour common to all sequence classes.
$seq = Math::NumSeq::PrimeFactorCount->new ()
$seq = Math::NumSeq::PrimeFactorCount->new (multiplicity => $str, prime_type => $str)
Create and return a new sequence object.
multiplicityis a string either
"repeated" count repeats of primes (the default) "distinct" count only distinct primes
prime_typeis a string either
"all" count all primes "odd" count only odd primes (ie. not 2) "4k+1" count only primes 4k+1 "4k+3" count only primes 4k+3 "twin" count only twin primes (P for which P+2 or P-2 also prime) "SG" count only Sophie Germain primes (P for which 2P+1 also prime) "safe" count only "safe" primes (P for which (P-1)/2 also prime)
"twin" counts both primes of each twin prime pair, so all of 3,5,7, 11,13, 17,19, etc.
$value = $seq->ith($i)
Return the number of prime factors in
This requires factorizing
$iand the current code has a hard limit of 2**32 on
$i, in the interests of not going into a near-infinite loop.
$bool = $seq->pred($value)
Return true if
$valueoccurs in the sequence, which means simply integer
$value >= 0.
Copyright 2010, 2011, 2012 Kevin Ryde
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