Computations and observations on congruence covering systems

Abstract

A $\text{covering system}$ is a collection of integer congruences such that every integer satisfies at least one congruence in the collection. A covering system is called $\text{distinct}$ if all of its moduli are distinct. An expansive literature has developed on covering systems since their introduction by Erdős. Here we provide a full classification of distinct covering systems with at most ten moduli, which we group together based on two forms of equivalence. As a consequence, we determine the minimum cardinality of a distinct covering system with all moduli exceeding $2$, which is $11$.

6 pages, one table, some expository portions removed, paper reorganized to focus on Propositions 1.2 and 3.2, to appear in Proceedings of INTEGERS 2023