Multifactorial

The multifactorial is a generalization of the double factorial, defining:
*\(n!! = n \cdot(n - 2) \cdot(n - 4) \cdot(n - 6)\ldots\)
*\(n!!! = n \cdot(n - 3) \cdot(n - 6) \cdot(n - 9)\ldots\)
*\(n!!!! = n \cdot(n - 4) \cdot(n - 8) \cdot(n - 12)\ldots\)
and so forth. For example, 10!!! = 10 7 4 1 = 280.
It is important to note that multifactorials should not be interpreted as nested factorials, e.g. \(n!! < (n!)!\) and \(n!!! < ((n!)!)!\). Multifactorials actually grow slower than normal factorials, so much slower than nested factorials.
== Sources ==
Category:Functions
Category:Factorials