English

An involution for a Catalan-tangent number identity

Combinatorics 2025-12-01 v1

Abstract

We provide an involution proof of a Catalan-tangent number identity arising from the study of peak algebra that was found by Aliniaeifard and Li. In the course, we find a new combinatorial identity for the tangent numbers T2n+1T_{2n+1}: k=0n(1)k(2n+12k)22n2kT2k+1=(1)nT2n+1. \sum_{k=0}^{n}(-1)^{k}{2n+1\choose 2k}2^{2n-2k}T_{2k+1}=(-1)^nT_{2n+1}. Moreover, we derive two different qq-analogs of the above identity from the combinatorial perspective.

Keywords

Cite

@article{arxiv.2511.22157,
  title  = {An involution for a Catalan-tangent number identity},
  author = {Dongsu Kim and Zhicong Lin},
  journal= {arXiv preprint arXiv:2511.22157},
  year   = {2025}
}

Comments

12 pages, 3 figures

R2 v1 2026-07-01T07:57:34.662Z