Falk Hüffner - cp's OEIS frontend

User: Falk Hüffner

Falk Hüffner has authored 2 sequences.

A267653 Number of unlabeled, connected graphs on n vertices which have no induced subgraph isomorphic to an R-graph.

1, 1, 2, 6, 21, 111, 818, 9825, 195759, 6622127, 368949015

Offset: 1

Falk Hüffner, Jan 19 2016

The R-graph has 6 vertices. 4 vertices form a cycle and both the other two vertices are adjacent to a single one of those 4.

F. Hüffner, tinygraph, software for generating integer sequences based on graph properties, version e8699da.

Cf. A079570, the same for the cricket graph (like an R-graph, but with a triangle instead of a 4-cycle).

A267602 Number of unlabeled, connected graphs on n vertices that are prime and have no induced subgraph isomorphic to a bull, a P5 or a P5-bar.

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0

Offset: 1

Falk Hüffner, Jan 18 2016

a(4) = 1 is the P_4, a(5) = 1 is the C_5, and a(n) = 2 for even n >= 6 are the unique prime bipartite chain graph on n vertices and its complement. - Falk Hüffner, Jan 18 2016

J. L. Fouquet, A Decomposition for a class of (P5,P5-bar)-free graphs, Discrete Math. 121 (1993) 75-83.

Cf. A079577 (without "prime" requirement)

cp's OEIS Frontend

User: Falk Hüffner

A267653 Number of unlabeled, connected graphs on n vertices which have no induced subgraph isomorphic to an R-graph.

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