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A091071
Number of normalizers of subgroups of the symmetric group on n points.
0
1, 1, 1, 2, 4, 5, 12, 19, 42, 72, 127, 196, 500
OFFSET
0,4
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.
EXAMPLE
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.
CROSSREFS
Cf. A000638 (subgroups of Sym(n)), A091070 (stabilizers of partial orders).
Sequence in context: A318780 A056984 A117556 * A353850 A050599 A281643
KEYWORD
hard,nonn
AUTHOR
Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004
STATUS
approved