English

Weighted Schreier-type Sets and the Fibonacci Sequence

Combinatorics 2024-05-31 v1 Number Theory

Abstract

For a finite set ANA\subset\mathbb{N} and kNk\in \mathbb{N}, let ωk(A)=iA,ik1\omega_k(A) = \sum_{i\in A, i\neq k}1. For each nNn\in \mathbb{N}, define ak,n = {EN:E=\mboxorωk(E)<minEmaxEn}.a_{k, n}\ =\ |\{E\subset \mathbb{N}\,:\, E = \emptyset\mbox{ or } \omega_k(E) < \min E\leqslant \max E\leqslant n\}|. First, we prove that ak,k+ = 2Fk+,\mboxforall0\mboxandk+2,a_{k,k+\ell} \ =\ 2F_{k+\ell},\mbox{ for all }\ell\geqslant 0\mbox{ and }k\geqslant \ell+2, where FnF_n is the nnth Fibonacci number. Second, we show that {EN:maxE=n+1,minE>ω2,3(E),\mboxandE2} = Fn,|\{E\subset \mathbb{N}\,:\, \max E = n+1, \min E > \omega_{2,3}(E), \mbox{ and }|E|\neq 2\}|\ =\ F_{n}, where ω2,3(E)=iE,i2,31\omega_{2,3}(E) = \sum_{i\in E, i\neq 2, 3}1.

Keywords

Cite

@article{arxiv.2405.19352,
  title  = {Weighted Schreier-type Sets and the Fibonacci Sequence},
  author = {Hung Viet Chu and Zachary Louis Vasseur},
  journal= {arXiv preprint arXiv:2405.19352},
  year   = {2024}
}

Comments

14 pages

R2 v1 2026-06-28T16:46:07.488Z