  The exponential functional of simple, symmetric random walks with negative
drift is an infinite polynomial $Y = 1 + \xi_1 + \xi_1 \xi_2 + \xi_1 \xi_2
\xi_3 + ...$ of independent and identically distributed non-negative random
variables. It has moments that are rational functions of the variables $\mu_k =
\ev(\xi^k) < 1$ with universal coefficients. It turns out that such a
coefficient is equal to the number of permutations with descent set defined by
the multiindex of the coefficient. A recursion enumerates all numbers of
permutations with given descent sets in the form of a Pascal-type triangle.
