permutations
Gives the number of k
permutations of a set of n
elements.
Syntax

permutations(n, k)

n
is a positive integer 
k
is a positive integer no greater thann

Description
The number of k
permutations of a set of n
elements is
permutations(n, k) = n! / (n − k)!
This is the number of distinct sequences of length k
that can be formed using the symbols from a set of cardinality n
.
Examples
permutations(70, 10)
1439561377475020800