moment: vector c(k1,...,kn) specifying the moment X1k1 ... Xnkn
current.matrix: upper-triangular integer matrix under consideration in recursion
current.cell: cell in current matrix under consideration in recursion
moment.rep: current set of representations; mult.moments adds each satisfying matrix to moment.rep
row_col: matrix giving rows and columns for square matrix for each cell
Details
Each row of the representation gives the exponents for a single product of covariance terms. For example, (1,2,0) represents S111 S122 S22**0, where the Sij are the covariances.
This function would normally only be called by callmultmoments.
Returns
moment representation, moment.rep, augmented with additional representations
References
K Phillips, Symbolic Computation of the Central Moments of the Multivariate Normal Distribution, Journal of Statistical Software, 2010.