fac_ui rewrote.

Niels Möller nisse at lysator.liu.se
Sat Dec 10 21:15:38 CET 2011

bodrato at mail.dm.unipi.it writes:

> mpz_bc_oddfac_1(x,n), likewise computes n! with every even factor removed;
> mpz_dsc_oddfac_1(x,n), computes the odd part of n!, asymptotically fast.

If you are using such building blocks, maybe it would make sense to
export a function for the "semi-factorial"? In my calculus course it was
denoted n!! = n (n-2) (n-4) ... (the product stopping at 1 for odd n and
2 for even n).

I don't remember off the top of my head in which context it was used,
but it must have appeared in some expansion of some not very exotic


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