This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A027842 #16 Jul 08 2025 17:56:02 %S A027842 1,7,34,227,1296,10576,77554,729379,7013419,77371042,910455096, %T A027842 11877617828,165087132666,2480783846184,39677415301224, %U A027842 675818886754115,12180498014887816,231893906693650507,4645789707491981892,97740610362119850762,2153888078209948673032 %N A027842 Number of subgroups of index n in fundamental group of a certain fiber space. %H A027842 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. %Y A027842 Cf. A027838, A027839, A027840, A060240. %K A027842 nonn %O A027842 1,2 %A A027842 _N. J. A. Sloane_ %E A027842 More terms from _Sean A. Irvine_, Dec 07 2019