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 A316498 #6 Jul 05 2018 02:08:12 %S A316498 1,3,4,7,3,13,3,15,6,10,3,32,3,10,13,26,3,20,3,25,13,10,3,75,5,10,8, %T A316498 25,3,48,3,37,13,10,10,50,3,10,13,60,3,48,3,25,20,10,3,135,5,17,13,25, %U A316498 3,27,10,60,13,10,3,127,3,10,20,48,10,48,3,25,13,38 %N A316498 Number of normal subgroups of the special linear group SL(2, Z_n). %o A316498 (GAP) Concatenation([1], List([2..20], n->Size(NormalSubgroups(SL(2, Integers mod n))))); %Y A316498 Cf. A000056, A066541. %K A316498 nonn %O A316498 1,2 %A A316498 _Andrew Howroyd_, Jul 04 2018