Factorial

The factorial function ($n!$) is a recursive mathematical function that produces factorials ($5\times 4\times 3\times \dots$) of size $n$.

Definition §

$$n!=\{\begin{array}{ll}n\times (n-1)!,& n>0\\ 1,& n\le 0\end{array}$$

For example, with 5!

$5!=5\times 4!=5\times 4\times 3!=5\times \dots 2\times =120$

Stirling’s Formula §