I have come across a paper that has suggested a formula for "NUMBER OF MULTINOMIAL COEFFICIENTS NOT DIVISIBLE BY A PRIME"; but I don't understand the notation.Please help. The formula is:
$ G(n,l,p)= \sum_{k=0}^m(l,p-1)^k\frac{a^k}{l}\prod_{i=k}^m(l-1,a_i) $
Link to the paper:http://www.jstor.org/pss/119039