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A160454
Number of isomorphism classes of 5-fold coverings of a connected graph with Betti number n.
2
1, 7, 161, 14721, 1730861, 207388305, 24883501301, 2985987361161, 358318118583341, 42998170050574305, 5159780357316368741, 619173642303122852601, 74300837069552376921821, 8916100448264989434407505, 1069932053790827570370392981
OFFSET
0,2
COMMENTS
Number of orbits of the conjugacy action of Sym(5) on Sym(5)^n [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
M. W. Hero and J. F. Willenbring, Stable Hilbert series as related to the measurement of quantum entanglement, Discrete Math., 309 (2010), 6508-6514.
J. H. Kwak and J. Lee, Isomorphism classes of graph bundles. Can. J. Math., 42(4), 1990, pp. 747-761.
A. Prasad, Equivalence classes of nodes in trees and rational generating functions, arXiv preprint arXiv:1407.5284 [math.CO], 2014.
Index entries for linear recurrences with constant coefficients, signature (155,-4670,59440,-374304,1152000,-1382400).
FORMULA
a(n+1) = 4^n + 5^n + 2 * 6^n + 8^n + 12^n + 120^n. - Álvar Ibeas, Mar 24 2015
G.f.: -(249792*x^5-159200*x^4+36984*x^3-3746*x^2+148*x-1) / ((4*x-1)*(5*x-1)*(6*x-1)*(8*x-1)*(12*x-1)*(120*x-1)). - Colin Barker, Mar 24 2015
MATHEMATICA
LinearRecurrence[{155, -4670, 59440, -374304, 1152000, -1382400}, {1, 7, 161, 14721, 1730861, 207388305}, 20] (* Harvey P. Dale, Apr 08 2016 *)
PROG
(PARI) Vec(-(249792*x^5-159200*x^4+36984*x^3-3746*x^2+148*x-1) / ((4*x-1)*(5*x-1)*(6*x-1)*(8*x-1)*(12*x-1)*(120*x-1)) + O(x^100)) \\ Colin Barker, Mar 24 2015
CROSSREFS
Fifth row of A160449.
Sequence in context: A320337 A214350 A208263 * A217241 A317727 A142163
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Nov 15 2009
EXTENSIONS
Name clarified and more terms added by Álvar Ibeas, Mar 24 2015
STATUS
approved