Factorial

Integer!

factorial(Integer, Integer)

Given an integer $n$ in the interval $[1,65535]$, returns the factorial, usually denoted by $n!$, defined as the product of all integers between 1 and $n$: $n!=1·2·3\cdots (n-1)·n$. By convention, $0!=1$.

Given two integers $n$ and $k$, returns the following computation: $n·(n-k)·(n-2k)\cdots a,\text{ with }1\le a<k$

Double factorial