nsimplex: Computes the number of points on a (p, n)-simplex lattice
Description
Computes the number of points on a (p, n)-simplex lattice; that is, the
number of p-part compositions of n. This gives the number of points in
the support space of a Multinomial(n, q) distribution, where
p == length(q).
Arguments p and n are replicated as necessary to have the length of the
longer of them.