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%I #12 Dec 08 2019 08:10:43
%S 1,31,301,6491,151711,6673555,362072313,26375525171,2384038557346,
%T 264381564291841,35133143655949285,5515729547285229215,
%U 1009373492449379396535,212997911098253654157543,51337590023914004777654131,14016616814681248497416279139
%N Number of subgroups of index n in fundamental group of a certain fiber space.
%H V. A. Liskovets and A. Mednykh, <a href="https://doi.org/10.1080/00927870008826924">Enumeration of subgroups in the fundamental groups of orientable circle bundles over surfaces</a>, Commun. in Algebra, 28, No. 4 (2000), 1717-1738.
%F a(n) = Sum_{m|n} A027840(m) * (n/m)^(2*m+2). - _Sean A. Irvine_, Dec 07 2019
%Y Cf. A027838, A027839, A027840.
%K nonn
%O 1,2
%A _N. J. A. Sloane_.
%E More terms from _Sean A. Irvine_, Dec 07 2019
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