English

A 920-block explicit construction guaranteeing a triple intersection with every 6-subset of [60]

Combinatorics 2026-01-13 v1

Abstract

We present an explicit family B\mathcal{B} of 920920 subsets of size 66 of [60]={1,,60}[60]=\{1,\dots,60\} with the property that every 66-subset S[60]S\subset[60] intersects at least one block BBB\in\mathcal{B} in at least three elements, i.e.\ SB3|S\cap B|\ge 3. The construction is purely combinatorial, based on a partition of the ground set into pairs and a pigeonhole argument. We also record a simple counting lower bound and discuss how different partitions of the ten base blocks affect the emergence of triple intersections.

Keywords

Cite

@article{arxiv.2601.06179,
  title  = {A 920-block explicit construction guaranteeing a triple intersection with every 6-subset of [60]},
  author = {Paulo Henrique Cunha Gomes},
  journal= {arXiv preprint arXiv:2601.06179},
  year   = {2026}
}