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
KEYWORD
hard,more,nonn
AUTHOR
Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004
STATUS
approved