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Number of unlabeled, connected graphs on n vertices with no induced subgraph isomorphic to a bull-graph.
2

%I #21 Mar 03 2020 10:27:24

%S 1,1,2,6,20,93,480,2960,19475,140851,1116717,10329833,121557264

%N Number of unlabeled, connected graphs on n vertices with no induced subgraph isomorphic to a bull-graph.

%C A bull-graph is formed by adding a 5th vertex to a 4-path adjacent only to the middle two vertices on the path.

%H C. De Simone and A. Sassano, <a href="https://doi.org/10.1016/0166-218X(93)90032-J">Stability number of bull- and chair-free graphs</a>, Discrete Appl. Math. 41 (1993) 121-129.

%H Travis Hoppe and Anna Petrone, <a href="https://github.com/thoppe/Encyclopedia-of-Finite-Graphs">Encyclopedia of Finite Graphs</a>

%H Falk Hüffner, <a href="https://github.com/falk-hueffner/tinygraph">tinygraph</a>, software for generating integer sequences based on graph properties, version ece94ef.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/BullGraph.html">Bull Graph</a>

%Y Cf. A244427 (no bull subgraph).

%K nonn,more

%O 1,3

%A _Jim Nastos_, Jan 24 2003

%E a(10)-a(13) added using tinygraph by _Falk Hüffner_, Jan 15 2016