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A091070 Number of automorphism groups of partial orders on n points. 1

%I

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

%N Number of automorphism groups of partial orders on n points.

%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)=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.

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

%K hard,more,nonn

%O 0,3

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

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Last modified September 21 16:31 EDT 2021. Contains 347598 sequences. (Running on oeis4.)