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%I #8 Nov 20 2023 04:24:42
%S 1,2,25,520,15150,567540,25986334,1406214816,87803248260,
%T 6213408758960,491423381371208,42958461746823376,4112928296979824348,
%U 428022362222941505760,48106759414197240877200,5807382441785322296139392
%N Number of labeled digraphs without isolated vertices and with n arcs.
%F a(n) = Sum_{m>=0} binomial(m*(m-1),n)/2^(m+1). Column sums of A054547.
%p seq(value(Sum(binomial(m*(m-1),n)/2^(m+1),m=0..infinity)),n=0..20); # _Vladeta Jovovic_, Aug 25 2006
%Y Cf. A054545, A053418 (unlabeled).
%K easy,nonn
%O 0,2
%A _Vladeta Jovovic_, Aug 22 2006
%E More terms from _Max Alekseyev_, Aug 23 2006
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