English

Binomial convolutions for rational power series

Combinatorics 2024-02-14 v2

Abstract

The binomial convolution of two sequences {an}\{a_n\} and {bn}\{b_n\} is the sequence whose nnth term is k=0n(nk)akbnk\sum_{k=0}^{n} \binom{n}{k} a_k b_{n-k}. If {an}\{a_n\} and {bn}\{b_n\} have rational generating functions then so does their binomial convolution. We discuss an efficient method, using resultants, for computing this rational generating function and give several examples involving Fibonacci and tribonacci numbers and related sequences. We then describe a similar method for computing Hadamard products of rational generating functions. Finally we describe two additional methods for computing binomial convolutions and Hadamard products of rational power series, one using symmetric functions and one using partial fractions.

Keywords

Cite

@article{arxiv.2304.10426,
  title  = {Binomial convolutions for rational power series},
  author = {Ira M. Gessel and Ishan Kar},
  journal= {arXiv preprint arXiv:2304.10426},
  year   = {2024}
}

Comments

20 pages

R2 v1 2026-06-28T10:12:41.133Z