This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A136719 #12 Feb 02 2020 17:41:01
%S A136719 1,3,27,432,10125,314928,12252303,573308928,31381059609,1968300000000,
%T A136719 139234453205859,10968475320188928,952427511967417317,
%U A136719 90388408459919044608,9308590679915771484375,1033947715493982426365952,123217926482311669202664753,15682720840457750419215679488
%N A136719 Number of labeled directed trees with n nodes.
%C A136719 A directed tree is a tree where each edge is assigned one or both directions.
%D A136719 F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 292 (4.1.58).
%H A136719 Andrew Howroyd, <a href="/A136719/b136719.txt">Table of n, a(n) for n = 1..200</a>
%H A136719 <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%F A136719 a(n) = A052756(n)/n.
%F A136719 a(n) = 3*(3*n)^(n-2). - _Andrew Howroyd_, Feb 02 2020
%o A136719 (PARI) seq(n)={Vec(serlaplace((-1/3)*lambertw(-3*x + O(x*x^n))/x))} \\ _Andrew Howroyd_, Feb 02 2020
%o A136719 (PARI) a(n) = {3*(3*n)^(n-2)} \\ _Andrew Howroyd_, Feb 02 2020
%Y A136719 Cf. A006965 (unlabeled version).
%K A136719 nonn
%O A136719 1,2
%A A136719 _Christian G. Bower_, Jan 18 2008
%E A136719 Terms a(16) and beyond from _Andrew Howroyd_, Feb 02 2020