

A160446


Number of isomorphism classes of nfold coverings of a connected graph with Betti number 4.


3



1, 16, 251, 14491, 1730861, 373486525, 128038522439, 65551419139302, 47785761199635528, 47785253957386480534, 63601854214623350663136, 109903723926415382728069729, 241458148813601665905147070195
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OFFSET

1,2


COMMENTS

Number of orbits of the conjugacy action of Sym(n) on Sym(n)^4 [Kwak and Lee, 2001].  Álvar Ibeas, Mar 24 2015


REFERENCES

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. 97161.


LINKS

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. 747761.


PROG

(Sage) [sum(p.aut()**3 for p in Partitions(n)) for n in range(1, 9)] # Álvar Ibeas, Mar 24 2015


CROSSREFS

Fifth column of A160449.
Sequence in context: A282312 A110394 A220459 * A317894 A228982 A158531
Adjacent sequences: A160443 A160444 A160445 * A160447 A160448 A160449


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Nov 12 2009


EXTENSIONS

Name clarified and more terms added by Álvar Ibeas, Mar 24 2015


STATUS

approved



