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Number of unilaterally connected digraphs with n labeled nodes.
(Formerly M3156)
6

%I M3156 #23 Jan 19 2022 17:25:25

%S 1,3,48,3400,955860,1034141596,4340689156440,71756043154026904,

%T 4716284688998245793376,1237457313794197125403483936,

%U 1297922676419612772784598299454784,5444329780242560941321703550018388707904,91342929096228825123968637168641318872709897472

%N Number of unilaterally connected digraphs with n labeled nodes.

%D V. Jovovic, 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="/A003029/b003029.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) Unilaterally(12) \\ See A057275. - _Andrew Howroyd_, Jan 19 2022

%Y The unlabeled version is A003088.

%Y Row sums of A057275.

%Y Cf. A003027, A003028, A003030, A049524, A049414.

%K nonn,nice,easy

%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