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%I #5 May 23 2015 16:33:13
%S 1,1,1,2,4,5,12,19,42,72,127,196,500
%N Number of normalizers of subgroups of the symmetric group on n points.
%D G. Pfeiffer, Counting Transitive Relations, preprint, 2004.
%H G. Pfeiffer, <a href="http://schmidt.nuigalway.ie/subgroups">Subgroups</a>.
%H 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 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 Cf. A000638 (subgroups of Sym(n)), A091070 (stabilizers of partial orders).
%K hard,nonn
%O 0,4
%A Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004
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