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A047864 Number of labeled bipartite graphs with n nodes. 10
1, 1, 2, 7, 41, 376, 5177, 103237, 2922446, 116011231, 6433447397, 498234407452, 54007795331921, 8213123246906761, 1756336596363006842, 528975889250504033527, 224688018516023267969441, 134708289561117007261966816 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

H. S. Wilf, Generatingfunctionology, Academic Press, NY, 1990, p. 80, Eq. 3.11.5.

LINKS

T. D. Noe, Table of n, a(n) for n=0..50

H. S. Wilf, Generatingfunctionology, 2nd edn., Academic Press, NY, 1994, p. 89, Eq. 3.11.5.

Eric Weisstein's World of Mathematics, n-Colorable Graph

S. R. Finch, Bipartite, k-colorable and k-colored graphs

FORMULA

E.g.f. = sqrt( e.g.f. for A047863 ).

MATHEMATICA

nn = 20; a = Sum[Sum[Binomial[n, k] 2^(k (n - k)), {k, 0, n}] x^n/n!, {n, 0, nn}]; Range[0, nn]! CoefficientList[Series[a^(1/2), {x, 0, nn}], x]  (* Geoffrey Critzer, Jan 15 2012 *)

CROSSREFS

Sequence in context: A101390 A113144 A006846 * A173916 A163921 A213434

Adjacent sequences:  A047861 A047862 A047863 * A047865 A047866 A047867

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified July 22 21:23 EDT 2014. Contains 244844 sequences.