scipy.special.factorialk#

scipy.special.factorialk(n, k, exact=True)[source]#

Multifactorial of n of order k, n(!!…!).

This is the multifactorial of n skipping k values. For example,

factorialk(17, 4) = 17!!!! = 17 * 13 * 9 * 5 * 1

In particular, for any integer n, we have

factorialk(n, 1) = factorial(n)

factorialk(n, 2) = factorial2(n)

Parameters:

nint: Calculate multifactorial. If n < 1 - k, the return value is 0. Otherwise if n <= 0, the return value is 1.
kint: Order of multifactorial.
exactbool, optional: If exact is set to True, calculate the answer exactly using integer arithmetic.

Returns:

Raises:

Examples

>>> from scipy.special import factorialk
>>> factorialk(5, 1, exact=True)
120
>>> factorialk(5, 3, exact=True)
10