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%I #16 Apr 25 2018 20:41:14
%S 1,1,6,68,1206,29982,981476,40515568,2044492988,123175320988,
%T 8697475219688,709097832452880,65934837808883016,6920436929999656936,
%U 812724019581549433520,105986960037601701495680
%N Number of digraphs with unlabeled (non-isolated) nodes and n labeled edges.
%D G. Labelle, Counting enriched multigraphs..., Discrete Math., 217 (2000), 237-248.
%D G. Paquin, Dénombrement de multigraphes enrichis, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004.
%H G. Paquin, <a href="/A038205/a038205.pdf">Dénombrement de multigraphes enrichis</a>, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004. [Cached copy, with permission]
%F E.g.f.: exp(-1) * Sum_{n>=0} (1+x)^(n^2-n) / n!. - _Paul D. Hanna_, Apr 25 2018
%F a(n) = n!*exp(-1) * Sum_{k>=sqrt(n)} binomial(k^2-k, n) / k!. - _Paul D. Hanna_, Apr 25 2018
%Y Cf. A014507.
%K nonn
%O 0,3
%A _Simon Plouffe_, gilbert(AT)lacim.uqam.ca (Gilbert Labelle).
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