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A057013 Number of conjugacy classes of subgroups of index n in free group of rank n. 9
1, 3, 41, 14120, 207009649, 193466859054994, 16390021452000128467345, 173238117954686651535535048940928, 300679800156605267097630253972085058107938561 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

J. H. Kwak and J. Lee, J. Graph Th., 23 (1996), 105-109.

V. A. Liskovets, Reductive enumeration under mutually orthogonal group actions, Acta Applic. Math., 52 (1998), 91-120.

R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.13(c), pp. 76, 112.

LINKS

Table of n, a(n) for n=1..9.

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.

Index entries for sequences related to groups

CROSSREFS

Cf. A057004-A057012.

Sequence in context: A239039 A228456 A238717 * A055755 A249046 A237661

Adjacent sequences:  A057010 A057011 A057012 * A057014 A057015 A057016

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

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Last modified October 17 05:23 EDT 2018. Contains 316275 sequences. (Running on oeis4.)