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Search: id:A000686
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| A000686 |
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Number of 4-colored labeled graphs on n nodes.
(Formerly M4449 N1884)
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+0
1
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| 1, 7, 85, 1777, 63601, 3882817, 403308865, 71139019777, 21276992674561, 10778161937857537, 9238819435213784065, 13390649605615389843457, 32796747486424209782108161, 135669064080920007649863745537
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Sequence represents 1/4 of the number of 4-colored labeled graphs on n nodes. Indeed, on p. 413 of the Read paper, column 4 is 4,28,340,7108,... - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 06 2004
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REFERENCES
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R. C. Read, The number of k-colored graphs on labeled nodes, Canad. J. Math., 12 (1960), 410-414.
R. C. Read, personal communication.
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LINKS
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S. R. Finch, Bipartite, k-colorable and k-colored graphs (4*A000686)
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FORMULA
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a(n)=(1/4)sum(binomial(n, k)*2^[k(n-k)]*b(k), k=0..n), where b(0)=1 and b(k)=3*A000685(k) for k > 0. - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 06 2004
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CROSSREFS
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Cf. A000683, A000685.
Sequence in context: A121020 A000424 A060237 this_sequence A102923 A092586 A048363
Adjacent sequences: A000683 A000684 A000685 this_sequence A000687 A000688 A000689
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KEYWORD
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nonn,easy,nice
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AUTHOR
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njas
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EXTENSIONS
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More terms from Pab Ter (pabrlos(AT)yahoo.com) and Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2004
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