OFFSET
1,3
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
KEYWORD
nonn,more
AUTHOR
Travis Hoppe and Anna Petrone, May 22 2014
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
STATUS
approved