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.

For example, the number of ways of shuffling 52 playing cards is 52! or nearly 10^68. 52 Factorial.

Last updated: 2012-11-23


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