Errera graph
| Errera graph | |
|---|---|
The Errera graph | |
| Named after | Alfred Errera |
| Vertices | 17 |
| Edges | 45 |
| Radius | 3 |
| Diameter | 4 |
| Girth | 3 |
| Automorphisms | 20 (D10) |
| Chromatic number | 4 |
| Chromatic index | 6 |
| Properties | Planar Hamiltonian |
| Table of graphs and parameters | |
In the mathematical field of graph theory, the Errera graph is a graph with 17 vertices and 45 edges. Alfred Errera published it in 1921 as a counterexample to Kempe's erroneous proof of the four color theorem; it was named after Errera by Hutchinson & Wagon (1998).