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Number of chordal bipartite graphs on n unlabeled vertices.
2

%I #7 Apr 10 2024 09:34:11

%S 1,2,3,7,13,34,84,270,912,3755,17169,90953,538858,3586559,26459702,

%T 215517278,1925402918,18785105127,199301164172

%N Number of chordal bipartite graphs on n unlabeled vertices.

%C A chordal bipartite graph is a bipartite graph with no induced cycles longer than 4-cycles. Note that this is not the same as a bipartite graph which is chordal, as that would exclude all cycles. This sequence includes disconnected graphs.

%H Brendan McKay, <a href="https://users.cecs.anu.edu.au/~bdm/nauty/">nauty software </a> that can generate these graphs.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Chordal_bipartite_graph">Chordal bipartite graph</a>.

%e For n=3, the three examples are the two disconnected graphs and the path.

%Y Cf. A371868, A371869.

%K nonn,hard,more

%O 1,2

%A _Brendan McKay_, Apr 09 2024