PERM _ _ _ _ _ _ _ _ _ _ _ _ operator
If <expression1> and <expression2> evaluate to positive integers, perm returns the number of permutations possible in selecting <expression1> objects from <expression2> objects. In other cases, an expression in the original operator is returned.
perm(1,1); 1 perm(3,5); 60 perm(-3,5); PERM(-3,5) perm(a,b); PERM(A,B)