# Selfridge, John L.

## Covering systems with big moduli ★★

\begin{problem} Does for every integer $N$ exist a \Def{covering system} with all moduli distinct and at least equal to~$N$? \end{problem}

Keywords: covering system

## Odd incongruent covering systems ★★★

\begin{conjecture} There is no \Def{covering system} whose moduli are odd, distinct, and greater than 1. \end{conjecture}

Keywords: covering system