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 A001051 #20 Feb 16 2025 08:32:22
%S A001051 1,3,1,5,1,5,1,7,1,5,1,8,1,5,1,7,1,5,1,7,1,5,1,10,1,5,1,7,1,5,1,7,1,5,
%T A001051 1,7,1,5,1,7,1,5,1,7,1,5,1,8,1,5,1,7,1,5,1,7,1,5,1,8,1,5,1,7,1,5,1,7,
%U A001051 1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,7,1,5,1,8
%N A001051 Number of subgroups of order n in orthogonal group O(3).
%H A001051 Antti Karttunen, <a href="/A001051/b001051.txt">Table of n, a(n) for n = 1..10000</a>
%H A001051 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/OrthogonalGroup.html">Orthogonal Group.</a>
%F A001051 Has period 1 5 1 7 except that a(2) = 3, a(4) = 5, a(12) = 8, a(24) = 10, a(48) = a(60) = a(120) = 8.
%t A001051 a[2] = 3; a[4] = 5; a[12] = 8; a[24] = 10; a[48] = a[60] = a[120] = 8; a[n_] := Switch[Mod[n, 4], 0, 7, 1, 1, 2, 5, 3, 1]; Table[a[n], {n, 1, 96}] (* _Jean-François Alcover_, Oct 15 2013 *)
%o A001051 (PARI) A001051(n) = if((12==n)||(48==n)||(60==n)||(120==n),8,if(24==n,10,if((4==n)||(2==n),1+n,[1,5,1,7][1+((n-1)%4)]))); \\ _Antti Karttunen_, Jan 15 2019
%Y A001051 The main sequences concerned with group theory are A000001, A000679, A001034, A001051, A001228, A005180, A000019, A000637, A000638, A002106, A005432, A051881.
%K A001051 nonn,easy,nice
%O A001051 1,2
%A A001051 _J. H. Conway_
%E A001051 Data section extended up to a(120) by _Antti Karttunen_, Jan 15 2019