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%I #11 Apr 13 2017 14:27:38
%S 1,0,2,6,50,510,7682,161406,4747010,194342910,11084390402,
%T 881008805886,97779099906050,15178191426486270,3302331237256396802,
%U 1008694542117649154046,433286992912494943469570
%N Number of labeled digraphs where every node has indegree 0 or outdegree 0 and no isolated nodes.
%C Also labeled graphs with 2-colored nodes with no isolated nodes where black nodes are only connected to white nodes and vice versa.
%F a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*A001831(k)
%F a(n) = Sum_{k=0..n} binomial(n, k)*(2^k-2)^(n-k). - _Vladeta Jovovic_, Apr 04 2003
%Y Cf. A001831 (binomial transform), A002031, A047863.
%K nonn
%O 0,3
%A _Christian G. Bower_, Dec 15 1999
%E Last 4 terms corrected by _Vladeta Jovovic_, Apr 04 2003