Approximating Factorials
Allen Klinger, © 2/21/2002
The calculation of factorial n, usually written by the symbols n! is found to most purposes by an estimate that accurately gives the order of magnitude. Stirling's approximation for the factorial is:
n! ~ n
n
e
-n
(2
p
n)
1/2
= (2
p
n)
1/2
(n/e)
n
21 Feb 2002 Version
http://www.cs.ucla.edu/~klinger/size.html
©2002 Allen Klinger