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A027839 Number of subgroups of index n in fundamental group of a certain fiber space. 4
1, 15, 124, 2431, 68766, 3025596 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

V. A. Liskovets and A. Mednykh, Enumeration of subgroups in the fundamental groups of orientable circle bundles over surfaces, Commun. in Algebra, 28, No. 4 (2000), 1717-1738.

R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.13(c), Eq. (5.125).

LINKS

Table of n, a(n) for n=1..6.

CROSSREFS

Cf. A027841, A027838, A027840.

Sequence in context: A038743 A181377 A264046 * A034271 A171220 A071080

Adjacent sequences:  A027836 A027837 A027838 * A027840 A027841 A027842

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified February 23 11:28 EST 2018. Contains 299571 sequences. (Running on oeis4.)