Covering systems with the sum of the reciprocals of the moduli close to $1$

Abstract

In 1952, H. Davenport posed the problem of determining a condition on the minimum modulus $m_0$ in a finite distinct covering system that would imply that the sum of the reciprocals of the moduli in the covering system is bounded away from $1$. In 1973, P. Erdos and J. Selfridge indicated that they believed that $m_0>4$ would suffice. We provide a proof that this is the case.