Double factorial and primorial

[bodrato at mail.dm.unipi.it]

Ciao,

Il Dom, 18 Dicembre 2011 9:13 am, Niels Möller ha scritto:
> Nice! Maybe it would be good with a slightly longer name, "2" is used
> for many other things. Maybe "mpz_double_fac_ui" is better?

_facfac_ or _dblfac_ ?

> I wonder for how large n it is practical to count the number of primes
> below n (without going to the trouble of multiplying them all together),
> is at as difficult as factoring, or even worse?

I believe that it is worse than factoring. By the way I implemented only
mpz_primorial_ui (as we have _fac_ui), i.e. I did not implement primorial
for general mpz_t numbers, but for unsigned int only.

Regards,
m

-- 
http://bodrato.it/software/combinatorics.html