:PROPERTIES:
:ID:       aed6b5dc-c2ec-4e8c-b793-538cd5d6e355
:END:
#+title: factorial
#+author: Preston Pan
#+options: num:nil
#+html_head: <link rel="stylesheet" type="text/css" href="../style.css" />

* Introduction
The factorial [[id:b1f9aa55-5f1e-4865-8118-43e5e5dc7752][function]] $n!: \mathbb{N} \rightarrow \mathbb{N}$ describes the amount of ways one can arrange $n$ differentiable objects. In practice:
\begin{align*}
0! = 1 \\
n! = (n - 1)! \times n
\end{align*}
is a [[id:8f265f93-e5fd-4150-a845-a60ab7063164][recursive]] definition of the factorial.