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A091070
Number of automorphism groups of partial orders on n points.
1
1, 1, 2, 3, 6, 8, 16, 21, 41, 57, 103, 140, 276
OFFSET
0,3
LINKS
G. Pfeiffer, Subgroups.
G. Pfeiffer, Counting Transitive Relations, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.2.
EXAMPLE
a(3)=3 because of the 5 partial orders on 3 points, 2 have trivial automorphism group, 2 have an automorphism of order 2 and one has the full symmetric group as its automorphism group; thus 3 different (conjugacy classes of) subgroups occur.
CROSSREFS
Cf. A000638 (subgroups of the symmetric group), A000112 (partial orders).
Sequence in context: A047001 A174021 A267007 * A133586 A141348 A334269
KEYWORD
hard,more,nonn
AUTHOR
Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004
STATUS
approved