We present two recursive enumeration formulas for the number of labelled essential graphs. The enumeration parameters of the first formula are the number of vertices, chain components, and cliques, while the enumeration parameters of the second formula are the number of vertices and cliques.Both formulas may be used to count the number of labelled essential graphs
with given number of vertices.
Citation
Bertran Steinsky. Enumeration of Labelled Essential Graphs[J], Ars Combinatoria, Volume 111. 485-494. .