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 A287889 #17 Sep 08 2022 08:46:19
%S A287889 1,12,4410,7560000,35626991400,357082280755200,6536573599765809600,
%T A287889 197543239414923257856000,9172025443146972656250000000,
%U A287889 619972004905097945232074342400000,58507834434071888178873434004530400000,7455351156359319047773396236777475276800000
%N A287889 Number of rooted labeled 4-cactus graphs on 3n+1 nodes.
%H A287889 Andrew Howroyd, <a href="/A287889/b287889.txt">Table of n, a(n) for n = 0..100</a>
%H A287889 Maryam Bahrani and Jérémie Lumbroso, <a href="http://arxiv.org/abs/1608.01465">Enumerations, Forbidden Subgraph Characterizations, and the Split-Decomposition</a>, arXiv:1608.01465 [math.CO], 2016.
%F A287889 a(n) = (3*n+1)^n*(3*n)!/(2^n*n!). - _Andrew Howroyd_, Feb 17 2020
%t A287889 Table[(3 n + 1)^n (3 n)! / (2^n n!), {n, 0, 15}] (* _Vincenzo Librandi_, Feb 19 2020 *)
%o A287889 (PARI) seq(n)={my(p=serlaplace(serreverse(x*exp(-x^3/2 + O(x^(3*n+1)))))); vector(n+1, k, polcoef(p, 3*k-2))} \\ _Andrew Howroyd_, Feb 17 2020
%o A287889 (Magma) [(3*n+1)^n*Factorial(3*n)/(2^n*Factorial(n)): n in [0..12]]; // _Vincenzo Librandi_, Feb 19 2020
%Y A287889 Cf. A034940, A287890, A287891, A287892.
%K A287889 nonn
%O A287889 0,2
%A A287889 _N. J. A. Sloane_, Jun 21 2017
%E A287889 a(0) changed and terms a(7) and beyond from _Andrew Howroyd_, Feb 17 2020