factorial

<mathematics> The mathematical function that takes a natural number, N, and returns the product of N and all smaller positive integers. This is written

	N! = N * (N-1) * (N-2) * ... * 1.

The factorial of zero is one because it is an empty product.

Factorial can be defined recursively as

	0! = 1
	N! = N * (N-1)!		, N > 0

The gamma function is the equivalent for real numbers.

Nearby terms:
FACT « fact « factor « factorial » FAD » failback » failover