%I A000686 M4449 N1884
%S A000686 1,7,85,1777,63601,3882817,403308865,71139019777,21276992674561,
%T A000686 10778161937857537,9238819435213784065,13390649605615389843457,
%U A000686 32796747486424209782108161,135669064080920007649863745537
%N A000686 Number of 4-colored labeled graphs on n nodes.
%C A000686 Sequence represents 1/4 of the number of 4-colored labeled graphs on 
               n nodes. Indeed, on p. 413 of the Read paper, column 4 is 4,28,340,
               7108,... - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 06 2004
%D A000686 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000686 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000686 R. C. Read, The number of k-colored graphs on labeled nodes, Canad. J. 
               Math., 12 (1960), 410-414.
%D A000686 R. C. Read, personal communication.
%H A000686 S. R. Finch, <a href="http://algo.inria.fr/bsolve/">Bipartite, k-colorable 
               and k-colored graphs</a> (4*A000686)
%F A000686 a(n)=(1/4)sum(binomial(n, k)*2^[k(n-k)]*b(k), k=0..n), where b(0)=1 and 
               b(k)=3*A000685(k) for k > 0. - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               May 06 2004
%Y A000686 Cf. A000683, A000685.
%Y A000686 Sequence in context: A121020 A000424 A060237 this_sequence A102923 A092586 
               A048363
%Y A000686 Adjacent sequences: A000683 A000684 A000685 this_sequence A000687 A000688 
               A000689
%K A000686 nonn,easy,nice
%O A000686 1,2
%A A000686 N. J. A. Sloane (njas(AT)research.att.com).
%E A000686 More terms from Pab Ter (pabrlos(AT)yahoo.com) and Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               May 05 2004