A091071 Number of normalizers of subgroups of the symmetric group on n points.
1, 1, 1, 2, 4, 5, 12, 19, 42, 72, 127, 196, 500
Offset: 0
Examples
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.
References
- G. Pfeiffer, Counting Transitive Relations, preprint, 2004.
Links
- G. Pfeiffer, Subgroups.
- G. Pfeiffer, Counting Transitive Relations, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.2.