English

The Erd\H{o}s-Selfridge problem with square-free moduli

Number Theory 2021-05-26 v1 Combinatorics

Abstract

A covering system is a finite collection of arithmetic progressions whose union is the set of integers. The study of covering systems with distinct moduli was initiated by Erd\H{o}s in 1950, and over the following decades numerous problems were posed regarding their properties. One particularly notorious question, due to Erd\H{o}s, asks whether there exist covering systems whose moduli are distinct and all odd. We show that if in addition one assumes the moduli are square-free, then there must be an even modulus.

Keywords

Cite

@article{arxiv.1901.11465,
  title  = {The Erd\H{o}s-Selfridge problem with square-free moduli},
  author = {Paul Balister and Béla Bollobás and Robert Morris and Julian Sahasrabudhe and Marius Tiba},
  journal= {arXiv preprint arXiv:1901.11465},
  year   = {2021}
}

Comments

17 pages

R2 v1 2026-06-23T07:28:28.228Z