Bilateral hypergeometric series

In mathematics, a bilateral hypergeometric series is a series Σan summed over all integers n, and such that the ratio In mathematics, a bilateral hypergeometric series is a series Σan summed over all integers n, and such that the ratio of two terms is a rational function of n. The definition of the generalized hypergeometric series is similar, except that the terms with negative n must vanish; the bilateral series will in general have infinite numbers of non-zero terms for both positive and negative n.