factorial - The product of an integer and all the integers below it
Derangements - SubfactorialsFree Derangements - Subfactorials Calculator - Calculates the number of derangements/subfactorial !n.
FactorialsFree Factorials Calculator - Calculates the following factorial items:
* A factorial of one number such as n!
* A factorial of a numerator divided by a factorial of a denominator such as n!m!/a!b!
* Double Factorials such as n!!
* Stirlings Approximation for n!
MultifactorialsFree Multifactorials Calculator - Calculates the multifactorial n!(m)
