A242790 Number of connected diamond-free graphs on n nodes.

1, 1, 2, 4, 11, 39, 165, 967, 7684, 87012, 1410465, 32640019

Offset: 1

Author

Travis Hoppe and Anna Petrone, May 22 2014

Keywords

• nonn
• more

Comments

An equivalent definition: Number of simple connected graphs with n nodes that are have no subgraph isomorphic to the diamond graph or the complete graph K_4. This is the same because a graph contains a diamond as a subgraph iff it contains a diamond or K_4 as induced subgraph. - Falk Hüffner, Jan 11 2015

Links

• Travis Hoppe and Anna Petrone, Encyclopedia of Finite Graphs
• Falk Hüffner, tinygraph, software for generating integer sequences based on graph properties, version ece94ef.
• Eric Weisstein's World of Mathematics, Diamond Graph

Crossrefs

Cf. A077269 (connected squarefree graphs).

Cf. also A242790 (diamond free graphs), A079574 (K_4 free graphs).

Extensions

Entry revised by N. J. A. Sloane, Jan 11 2016

a(11) and a(12) added using tinygraph by Falk Hüffner, Jan 15 2016