Graphs without a 3-connected subgraph are 4-colorable

Édouard Bonnet, Carl Feghali, Tung Nguyen +4

In 1972, Mader showed that every graph without a 3-connected subgraph is 4-degenerate and thus 5-colorable}. We show that the number 5 of colors can be replaced by 4, which is best…