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 A091071 #5 May 23 2015 16:33:13 %S A091071 1,1,1,2,4,5,12,19,42,72,127,196,500 %N A091071 Number of normalizers of subgroups of the symmetric group on n points. %D A091071 G. Pfeiffer, Counting Transitive Relations, preprint, 2004. %H A091071 G. Pfeiffer, <a href="http://schmidt.nuigalway.ie/subgroups">Subgroups</a>. %H A091071 G. Pfeiffer, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL7/Pfeiffer/pfeiffer6.html">Counting Transitive Relations</a>, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.2. %e A091071 a(3)=2 because of the 4 (conjugacy classes of) subgroups of Sym(3) only 2 (Sym(2) and Sym(3)) are normalizers of subgroups. %Y A091071 Cf. A000638 (subgroups of Sym(n)), A091070 (stabilizers of partial orders). %K A091071 hard,nonn %O A091071 0,4 %A A091071 Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004