Multinomial​(System.​Collections.​Generic.​List{AngouriMath.​Entity})

multinomial(k_1, ..., k_m): (k_1 + ... + k_m)! / (k_1! ... k_m!), the number of
ways to put k_1 + ... + k_m things into groups of those sizes. It is written in the
factorial, which is the gamma function away from the whole numbers, so it is symmetric in its
arguments everywhere and has no value where an argument or their sum is a negative integer.
It is not the product of binomial coefficients the multinomial theorem factors it into:
binomial is 0 at a negative whole lower index, and that product depends on the order
of the arguments there.
https://github.com/asc-community/AngouriMath/issues/2182