The double factorial is a generalization of the usual Factorial defined by
(1) |
There are many identities relating double factorials to Factorials. Since
(2) |
(3) |
(4) |
(5) |
(6) |
(7) |
(8) |
(9) |
(10) |
The double factorial is a special case of the Multifactorial.
See also Factorial, Multifactorial
References
Sloane, N. J. A. Sequence
A006882/M0876
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.
The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.
© 1996-9 Eric W. Weisstein