A091073 Number of transitive relations on n unlabeled points.

1, 2, 8, 39, 242, 1895, 19051, 246895, 4145108, 90325655, 2555630036, 93810648902, 4461086120602, 274339212258846, 21775814889230580, 2226876304576948549

Offset: 0

Author

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

Keywords

• hard
• nonn
• nice

Comments

a(13)-a(15) are from Brinkmann's and McKay's paper. - Vladeta Jovovic, Jan 07 2006

Links

• Gunnar Brinkmann and Brendan D. McKay, Counting unlabelled topologies and transitive relations.
• Gunnar Brinkmann and Brendan D. McKay, Counting Unlabelled Topologies and Transitive Relations, Journal of Integer Sequences, Vol. 8 (2005), Article 05.2.1.
• G. Pfeiffer, Counting Transitive Relations, preprint, 2004.
• G. Pfeiffer, Counting Transitive Relations, Journal of Integer Sequences, Vol. 7 (2004), Article 04.3.2.

Crossrefs

Cf. A079265 (antisymmetric transitive relations), A001930 (reflexive transitive relations), A000112 (partial orders), A006905 (labeled transitive relations).

Extensions

More terms from Vladeta Jovovic, Jan 07 2006