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

Author

N. J. A. Sloane, Nov 12 2009

Keywords

• nonn

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.

Crossrefs

Fifth column of A160449.

Programs

Sage

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

Extensions

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