The ChvatalGraph() command constructs the Chvátal graph, a 4-regular graph with 12 vertices and 18 edges. Its chromatic number is 4.

The Chvátal graph was first described by Václav Chvátal.

with(GraphTheory):

with(SpecialGraphs):

C := ChvatalGraph();

$C≔\mathrm{Graph\; 1:\; an\; undirected\; graph\; with\; 12\; vertices\; and\; 24\; edges}$

ChromaticNumber(C);

$4$

G := AutomorphismGroup(C);

$G≔⟨\left(1\,3\right)\left(2\,11\right)\left(4\,8\right)\left(5\,6\right)\left(7\,12\right)\left(9\,10\right)\,\left(1\,2\,12\,8\right)\left(3\,4\,7\,11\right)\left(5\,9\,10\,6\right)⟩$

GroupTheory:-GroupOrder(G);

$8$

DrawGraph(C);

"Chvátal graph", Wikipedia. http://en.wikipedia.org/wiki/Chvatal_graph

The GraphTheory[SpecialGraphs][ChvatalGraph] command was introduced in Maple 2017.

For more information on Maple 2017 changes, see Updates in Maple 2017.