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 A316537 #13 Jul 10 2018 18:43:23
%S A316537 1,5,13,28,49,73,116,176,202,265,378,464,550,636,842,936,1041,1183,
%T A316537 1486,1712,2082,2055,2120,3088,2114,3023,2503,4200,4238,4862,4902,
%U A316537 4648,6564,5749,7434,7688,6331,8190,9880,11344,10172,12066,9378,13224,14168,11612
%N A316537 Number of cyclic subgroups of the group SL(2, Z(n)), counting conjugates as distinct.
%H A316537 Andrew Howroyd, <a href="/A316537/b316537.txt">Table of n, a(n) for n = 1..100</a>
%F A316537 a(n) = Sum_{k=1..A316563(n)} 1/phi(A316564(n, k)).
%e A316537 Case n=2: generators of the 5 cyclic groups are:
%e A316537 [ 1 0 ] [0 1] [1 0] [1 1] [0 1]
%e A316537 [ 0 1 ] [1 0] [1 1] [0 1] [1 1]
%o A316537 (GAP) Concatenation([1], List([2..10], n->Sum( Filtered( ConjugacyClassesSubgroups( SL(2, Integers mod n)), x->IsCyclic( Representative(x))), Size)));
%o A316537 (PARI)
%o A316537 MatOrder(M)={my(id=matid(#M), k=1, N=M); while(N<>id, k++;N=N*M); k}
%o A316537 a(n)={sum(a=0, n-1, sum(b=0, n-1, sum(c=0, n-1, sum(d=0, n-1, my(M=Mod([a, b; c, d], n)); if(matdet(M)==1, 1/eulerphi(MatOrder(M)))))))}
%Y A316537 Cf. A000056, A062314, A316536, A316553, A316560, A316563, A316564.
%K A316537 nonn
%O A316537 1,2
%A A316537 _Andrew Howroyd_, Jul 06 2018