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A005142
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Number of connected bipartite graphs with n nodes.
(Formerly M2501)
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18
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1, 1, 1, 3, 5, 17, 44, 182, 730, 4032, 25598, 212780, 2241730, 31193324, 575252112, 14218209962, 472740425319, 21208887576786, 1286099113807999, 105567921675718772
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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COMMENTS
| Also, the number of unlabeled connected bicolored graphs having n nodes; the color classes may be interchanged. - R. W. Robinson.
Also, for n>1, number of connected triangle-free graphs on n nodes with chromatic number 2. - Keith M. Briggs, Mar 21 2006 (cf. A116079).
Also, first diagonal of triangle in A126736.
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REFERENCES
| R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.
R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
P. Steinbach, Field Guide to Simple Graphs. Design Lab, Albuquerque NM, 1990.
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LINKS
| Keith M. Briggs, Combinatorial Graph Theory
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Eric Weisstein's World of Mathematics, n-Chromatic Graph
Eric Weisstein's World of Mathematics, n-Colorable Graph
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CROSSREFS
| Cf. A033995, A116079.
Sequence in context: A113275 A001572 A131342 * A165452 A106063 A006483
Adjacent sequences: A005139 A005140 A005141 * A005143 A005144 A005145
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from R. C. Read (rcread(AT)math.uwaterloo.ca).
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