Wheels in planar graphs and Hajós graphs
Wheels in planar graphs and Hajós graphs
Abstract It was conjectured by Hajós that graphs containing no ‐subdivision are 4‐colorable. Previous results show that any possible minimum counterexample to Hajós' conjecture, called Hajós graph, is 4‐connected but not 5‐connected. In this paper, we show that if a Hajós graph admits a 4‐cut or 5‐cut with a planar …