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Search: id:A126750
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| A126750 |
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Number of 2-connected (or biconnected) graphs on n nodes with chromatic number 2. |
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+0
2
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| 0, 0, 0, 1, 1, 5, 8, 42, 146, 956, 6643, 65921, 818448, 13442572
(list; graph; listen)
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OFFSET
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1,6
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COMMENT
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Equally, number of 2-connected (or biconnected) bipartite graphs on n nodes.
Also number of biconnected triangle-free graphs on n nodes with chromatic number 2, since chromatic number 2 implies triangle-free. - Gordon Royle, Apr 11 2007
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REFERENCES
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C. J. Colbourn and C. Huybrechts, Fully gated graphs,: recognition and convex operations, Discrete Math., 308 (2008), 5184-5195.
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LINKS
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Keith M. Briggs, Combinatorial Graph Theory
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CROSSREFS
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A diagonal of triangle in A126749.
Sequence in context: A151349 A073930 A130223 this_sequence A109292 A117474 A165716
Adjacent sequences: A126747 A126748 A126749 this_sequence A126751 A126752 A126753
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Feb 18 200, Oct 01 2008
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