%I A000608 M2864 N1152
%S A000608 1,1,1,3,10,44,238,1650,14512,163341,2360719,43944974,1055019099,
%T A000608 32664984238,1303143553205,66900392672168,4413439778321689
%N A000608 Number of connected partially ordered sets with n unlabeled elements.
%D A000608 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.
%D A000608 G. Melan\c{c}on, personal communication.
%D A000608 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000608 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000608 J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, 
               Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.
%H A000608 Gunnar Brinkmann and Brendan D. McKay, <a href="http://cs.anu.edu.au/
               ~bdm/papers/topologies.pdf">Counting unlabeled topologies and transitive 
               relations</a>.
%H A000608 P. J. Cameron, <a href="http://www.cs.uwaterloo.ca/journals/JIS/index.html">
               Sequences realized by oligomorphic permutation groups</a>, J. Integ. 
               Seqs. Vol. 3 (2000), #00.1.5.
%H A000608 N. J. A. Sloane, <a href="transforms.txt">Transforms</a>
%H A000608 <a href="Sindx_Pos.html#posets">Index entries for sequences related to 
               posets</a>
%Y A000608 Inverse Euler transform of A000112.
%Y A000608 Sequence in context: A026682 A096804 A113059 this_sequence A009648 A007125 
               A102911
%Y A000608 Adjacent sequences: A000605 A000606 A000607 this_sequence A000609 A000610 
               A000611
%K A000608 hard,nonn,nice
%O A000608 0,4
%A A000608 N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe, J. A. Wright
%E A000608 More terms from Christian Bower (bowerc(AT)usa.net), who pointed out 
               connection with A000112, Jan 21 1998 and Dec 12 2001
%E A000608 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 04 2006; corrected 
               Jan 15 2006