Returns the number of ways to choose some number of objects from a pool of a given size of objects, considering order.
n- The size of the pool of objects to choose from.
k- The number of objects to choose.
PERMUTis the standard combinatorics function typically notated nPk. This is similar to
COMBINexcept in permutations, the order of selection is considered rather than simply the resultant selected subset.
MULTINOMIAL: Returns the factorial of the sum of values divided by the product of the values' factorials.
FACTDOUBLE: Returns the "double factorial" of a number.
FACT: The FACT function returns the factorial of a number.
COMBIN: The COMBIN function returns the number of ways to choose some number of objects from a pool of a given size of objects.