Definition 1. The factorial of $n \in \N$, written $n!$, is defined recursively:
- \[0! = 1.\]
-
For all $n \in \N^+$,
\[n! = (n - 1)! \cdot n.\]
Note. For $n \in \N^+$ we have
\[n! = \prod_{k = 1}^n k.\]Pub Mar 22, 2026 Up Jun 20, 2026
Definition 1. The factorial of $n \in \N$, written $n!$, is defined recursively:
For all $n \in \N^+$,
\[n! = (n - 1)! \cdot n.\]Note. For $n \in \N^+$ we have
\[n! = \prod_{k = 1}^n k.\]