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A160446
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Number of isomorphism classes of n-fold coverings of a connected graph with Betti number 4.
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3
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1, 16, 251, 14491, 1730861, 373486525, 128038522439, 65551419139302, 47785761199635528, 47785253957386480534, 63601854214623350663136, 109903723926415382728069729, 241458148813601665905147070195
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OFFSET
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1,2
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COMMENTS
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Number of orbits of the conjugacy action of Sym(n) on Sym(n)^4 [Kwak and Lee, 2001]. - Álvar Ibeas, Mar 24 2015
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REFERENCES
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J. H. Kwak and J. Lee, Enumeration of graph coverings, surface branched coverings and related group theory, in Combinatorial and Computational Mathematics (Pohang, 2000), ed. S. Hong et al., World Scientific, Singapore 2001, pp. 97-161.
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LINKS
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Álvar Ibeas, Table of n, a(n) for n = 1..60
J. H. Kwak and J. Lee, Isomorphism classes of graph bundles. Can. J. Math., 42(4), 1990, pp. 747-761.
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PROG
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(Sage) [sum(p.aut()**3 for p in Partitions(n)) for n in range(1, 9)] # Álvar Ibeas, Mar 24 2015
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CROSSREFS
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Fifth column of A160449.
Sequence in context: A282312 A110394 A220459 * A317894 A228982 A158531
Adjacent sequences: A160443 A160444 A160445 * A160447 A160448 A160449
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Nov 12 2009
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EXTENSIONS
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Name clarified and more terms added by Álvar Ibeas, Mar 24 2015
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STATUS
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approved
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