0,3

a(13)-a(16) from Brinkmann's and McKay's paper, sent by Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 04 2006

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

Gunnar Brinkmann and Brendan D. McKay, Counting Unlabeled Topologies and Transitive Relations, Journal of Integer Sequences, Vol. 8 (2005), Article 05.2.1.

K. K.-H. Butler and G. Markowsky, Enumeration of finite topologies, Proc. 4th S-E Conf. Combin., Graph Theory, Computing, Congress. Numer. 8 (1973), 169-184.

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 218 (but the last entry is wrong).

J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.

J. A. Wright, personal communication.

For further references concerning the enumeration of topologies and posets see under A000112 and A001035.

Moussa Benoumhani, The Number of Topologies on a Finite Set, Journal of Integer Sequences, Vol. 9 (2006), Article 06.2.6.

Gunnar Brinkmann and Brendan D. McKay, Counting unlabeled topologies and transitive relations.

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

S. R. Finch, Transitive relations, topologies and partial orders

G. Pfeiffer, Counting Transitive Relations, preprint, 2004.

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

D. Rusin, More info and references

N. J. A. Sloane, Classic Sequences

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Cf. A000798 (labeled topologies), A001035 (labeled posets), A001930 (unlabeled topologies), A000112 (unlabeled posets), A006057, A001928, A001929.

Sequence in context: A098742 A009212 A153344 this_sequence A049425 A012584 A101899

Adjacent sequences: A001927 A001928 A001929 this_sequence A001931 A001932 A001933

nonn,hard,nice

N. J. A. Sloane (njas(AT)research.att.com).

a(8)-a(12) from Goetz Pfeiffer (goetz.pfeiffer(AT)nuigalway.ie), Jan 21 2004