We derive a combinatorial identity which is useful in studying the
distribution of Fourier coefficients of L-functions by allowing us to pass from
knowledge of moments of the coefficients to the distribution of the
coefficients.Comment: This paper contains the proof of a combinatorial identity used to
study effective equidistribution laws for the Fourier coefficients of
elliptic curve L-functions investigated by the first two authors in
http://arxiv.org/abs/1004.275
