Wolfram Research
Wolfram Math World: Derangements
This MathWorld page discusses derangements, which are permutations in which no elements appear in their "natural" places. Includes helpful examples and formulas for calculating possible derangements and provides helpful examples.
Wolfram Research
Wolfram Math World: Topics of Permutation
This MathWorld site is a lite to link to a multitude of sites involving permutations. Look through to find your specific needs. If you are looking at this site with regards to a probability and statisics class you will probably want to...