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%I M3157 #35 Apr 14 2023 10:52:39
%S 1,3,51,3614,991930,1051469032,4366988803688,71895397383029040,
%T 4719082081411731363408,1237678715644664931691596416,
%U 1297992266840866792981316221144960,5444416466164313011147841248189209354496,91343356480627224177654291875698256656613808896
%N Number of digraphs on n labeled nodes with a source.
%C Here a source is a node that is connected by a directed path to every other node in the digraph (but does not necessarily have indegree zero). - _Geoffrey Critzer_, Apr 14 2023
%D V. Jovovic and G. Kilibarda, Enumeration of labeled initially-finally connected digraphs, Scientific review, Serbian Scientific Society, 19-20 (1996) 237-247.
%D R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Andrew Howroyd, <a href="/A003028/b003028.txt">Table of n, a(n) for n = 1..50</a>
%H V. Jovovic and G. Kilibarda, <a href="http://dx.doi.org/10.1016/S0012-365X(00)00112-6">Enumeration of labeled quasi-initially connected digraphs</a>, Discrete Math., 224 (2000), 151-163.
%o (PARI) Initially(12) \\ See A057274. - _Andrew Howroyd_, Jan 11 2022
%Y The unlabeled version is A051421.
%Y Row sums of A057274.
%Y Column k=1 of A361579.
%Y Cf. A003027, A003029, A003030, A049524, A049414, A350792.
%K nonn,easy,nice
%O 1,2
%A _N. J. A. Sloane_
%E Corrected and extended by _Vladeta Jovovic_, Goran Kilibarda
%E Terms a(12) and beyond from _Andrew Howroyd_, Jan 11 2022
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