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%I #11 Dec 06 2019 21:48:45
%S 1,7,22,111,486,3772,29142,275871,2830459,32028882,392744078,
%T 5201524044,73943424582,1123603726896,18176728661832,311951284854975,
%U 5661698774848910,108355867352001811,2181096921557783966,46066653293892718506,1018705098450761473704
%N Number of subgroups of index n in fundamental group of a certain fiber space.
%D 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.
%D R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.13(c), Eq. (5.125).
%F a(n) = Sum_{m|n} A003319(m+1) * (n/m)^(m+1). - _Sean A. Irvine_, Dec 06 2019
%Y Cf. A027841, A027839, A027840.
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E More terms from _Sean A. Irvine_, Dec 06 2019
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