On Minimal Triangle-Free \(5\)-Chromatic Graphs

Charles M. Grinstead1, Matthew Katinsky1, David Van Stone1
1Department of Mathematics Swarthmore College Swarthmore, PA 19081 U.S.A.

Abstract

Avis has shown that the number of vertices of a minimal triangle-free \(5\)-chromatic graph is no fewer than \(19\). Mycielski has shown that this number is no more than \(23\). In this paper, we improve these bounds to \(21\) and \(22\), respectively.