English

A sharper log-convexity inequality for Bell numbers

Combinatorics 2026-06-29 v1

Abstract

We prove a stronger version of the log-convexity inequality for the Bell numbers BnB_n. In particular, for n5n\ge 5, we have Bn+1Bn1(Bn)2i=1nFi(Bni)2, B_{n+1}B_{n-1} - (B_n)^2 \ge \sum_{i=1}^{n} F_i (B_{n-i})^2, where FiF_i is the ii-th Fibonacci number with F0=F1=1F_0=F_1=1. The simple proof is mostly combinatorial with elementary inequalities.

Keywords

Cite

@article{arxiv.2606.29884,
  title  = {A sharper log-convexity inequality for Bell numbers},
  author = {Vuong Bui},
  journal= {arXiv preprint arXiv:2606.29884},
  year   = {2026}
}

Comments

7 pages; comments are welcome