Multifactorial number

Definition

A Factorial number is defined by the product

$n!=1\cdot 2\cdot 3\cdots (n-2)\cdot (n-1)\cdot n$

for $n\ge 1$.

A Multifactorial number is denoted by

$n!!=(n)\cdot (n-2)\cdot (n-4)\cdots$

$n!!!=(n)\cdot (n-3)\cdot (n-6)\cdots$

and so on.

To clarify and make reading easier $n!!!!!$ is displayed as $n{!}_5$.

See also

• Multifactorial prime

External links

• Multifactorials