Combinatorial analysis of integer power product expansions

H. Gingold1, Jocelyn Quaintance2
1WEST VIRGINIA UNIVERSITY, DEPARTMENT OF MATHEMATICS, MORGANTOWN WV 26506, USA,
2UNIVERSITY OF PENNSYLVANIA, DEPARTMENT OF COMPUTER SCIENCE, PHILADELPHIA PA 19104, USA,

Abstract

Let \( f(x) = 1 + \sum_{n=1}^\infty a_n x^n \) be a formal power series with complex coefficients. Let \( \{r_n\}_{n=1}^\infty \) be a sequence of nonzero integers. The Integer Power Product Expansion of \( f(x) \), denoted ZPPE, is \( \prod_{k=1}^\infty (1 + w_k x^k)^{r_k} \). Integer Power Product Expansions enumerate partitions of multi-sets. The coefficients \( \{w_k\}_{k=1}^\infty \) themselves possess interesting algebraic structure. This algebraic structure provides a lower bound for the radius of convergence of the ZPPE and provides an asymptotic bound for the weights associated with the multi-sets.

Keywords: Power products, generalized power products, generalized inverse power products, power series, partitions, compositions, multi-sets, analytic functions, expansions, convergence, asymptotics.