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A242790 Number of connected diamond-free graphs on n nodes. 11
1, 1, 2, 4, 11, 39, 165, 967, 7684, 87012, 1410465, 32640019 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..12.

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).

Sequence in context: A216810 A065851 A173938 * A013044 A110577 A012948

Adjacent sequences:  A242787 A242788 A242789 * A242791 A242792 A242793

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

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Last modified February 23 14:31 EST 2020. Contains 332163 sequences. (Running on oeis4.)