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A000683
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Number of 2-colored labeled graphs on n nodes.
(Formerly M4238 N1770)
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11
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0, 1, 6, 40, 360, 4576, 82656, 2122240, 77366400, 4002843136, 293717546496, 30558458490880, 4505780560619520, 941417163728674816, 278628902101315608576, 116805328001281573519360
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 18, table 1.5.1, column 2 (divided by 2).
R. C. Read, The number of k-colored graphs on labeled nodes, Canad. J. Math., 12 (1960), 410-414.
R. C. Read, personal communication.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..50
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FORMULA
| Reference gives generating function.
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MATHEMATICA
| maxn = 16; t[_, 1] = 1; t[n_, k_] := t[n, k] = Sum[Binomial[n, j]*2^(j*(n - j))*t[j, k - 1]/k, {j, 1, n - 1}]; a[n_] := t[n, 2]/2; Table[a[n], {n, 1, maxn}] (* From Jean-François Alcover, Sep 21 2011 *)
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CROSSREFS
| a(n)=(A047863(n)-2)/4. A diagonal of A058843.
Sequence in context: A006387 A014481 A184266 * A143342 A084270 A053677
Adjacent sequences: A000680 A000681 A000682 * A000684 A000685 A000686
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 02 2000
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