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URL: https://oeis.org/A057006

⇱ A057006 - OEIS

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A057006
Number of conjugacy classes of subgroups of index n in free group of rank 3.
4
1, 7, 41, 604, 13753, 504243, 24824785, 1598346352, 129958211233, 13030565312011, 1579721338432537, 227804599861102676, 38541084552054952009, 7560534755192908672087, 1702288146755359962223409
OFFSET
1,2
REFERENCES
R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.13(c), pp. 76, 112.
LINKS
J. B. Geloun and S. Ramgoolam, Counting Tensor Model Observables and Branched Covers of the 2-Sphere, arXiv preprint arXiv:1307.6490 [hep-th], 2013.
Joseph Ben Geloun and Sanjaye Ramgoolam, All-orders asymptotics of tensor model observables from symmetries of restricted partitions, arXiv:2106.01470 [hep-th], 2021.
J. H. Kwak and J. Lee, Enumeration of connected graph coverings, J. Graph Th., 23 (1996), 105-109.
J. H. Kwak and J. Lee, Enumeration of graph coverings and surface branched coverings, Lecture Note Series 1 (2001), Com^2MaC-KOSEF, Korea. See chapter 3.
V. A. Liskovets, Reductive enumeration under mutually orthogonal group actions, Acta Applic. Math., 52 (1998), 91-120.
P. Vrana, On the algebra of local unitary invariants of pure and mixed quantum states, J. Phys A: Math. Theor. 44 (2011) 225304 doi:10.1088/1751-8113/44/22/225304, Table 2.
CROSSREFS
Cf. A057004-A057013. Inverse Euler transform of A152612.
Sequence in context: A356129 A053676 A002701 * A144747 A176090 A183064
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 09 2000
EXTENSIONS
More terms from Francisco Salinas (franciscodesalinas(AT)hotmail.com), Dec 25 2001
STATUS
approved