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.

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

1,6

Comments

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

Links

Table of n, a(n) for n=1..87.

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

Crossrefs

Cf. A079577 (without "prime" requirement)

Sequence in context: A101227 A277162 A230103 * A021499 A176742 A010673

Adjacent sequences: A267599 A267600 A267601 * A267603 A267604 A267605

Keyword

nonn,easy

Author

Falk Hüffner, Jan 18 2016

Status

approved