%I A001928 M1655 N0648
%S A001928 1,1,2,6,21,94,512,3485,29515,314474,4255727,73831813,1653083021,
%T A001928 47941962135,1803010446411,87882300251730,5543501326580737
%N A001928 Number of connected topologies with n unlabeled nodes.
%D A001928 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001928 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001928 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 A001928 J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, 
               Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.
%D A001928 J. A. Wright, personal communication.
%H A001928 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.
%F A001928 Inverse Euler transform of A001930. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Jan 06 2006
%Y A001928 Cf. A001929, A001930.
%Y A001928 Sequence in context: A033540 A147719 A115089 this_sequence A005638 A008988 
               A061232
%Y A001928 Adjacent sequences: A001925 A001926 A001927 this_sequence A001929 A001930 
               A001931
%K A001928 nonn
%O A001928 0,3
%A A001928 N. J. A. Sloane (njas(AT)research.att.com).
%E A001928 More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 06 2006