A091070 Number of automorphism groups of partial orders on n points.

1, 1, 2, 3, 6, 8, 16, 21, 41, 57, 103, 140, 276

Offset: 0

Author

Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004

Keywords

• hard
• more
• nonn

Examples

			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.
		

Links

• G. Pfeiffer, Subgroups.
• G. Pfeiffer, Counting Transitive Relations, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.2.

Crossrefs

Cf. A000638 (subgroups of the symmetric group), A000112 (partial orders).