A160446 Number of isomorphism classes of n-fold coverings of a connected graph with Betti number 4.

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

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. 97-161.

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. 747-761.

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