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 A356290 #4 Aug 02 2022 06:40:19
%S A356290 1,5,31,200,1309,8627,57082,378648,2516111,16740913,111494801,
%T A356290 743137984,4956359312,33074272702,220810039566,1474764797488,
%U A356290 9853307017341,65853733243281,440255398634199,2944041287677060,19691951641479427,131744163990056479,881586559906575688
%N A356290 a(n) = Sum_{k=0..n} binomial(3*n, n-k) * v(k), where v(k) is the number of overpartitions of n (A015128).
%F A356290 a(n) ~ c * 3^(3*n + 1/2) / (sqrt(Pi*n) * 2^(2*n + 1)), where c = Sum_{j>=0} v(j)/2^j = 8.2559879357782500655441408494322731265270016167882303456037...
%t A356290 Table[Sum[Sum[PartitionsP[k-j]*PartitionsQ[j], {j, 0, k}] * Binomial[3*n, n-k], {k, 0, n}], {n, 0, 30}]
%Y A356290 Cf. A015128, A266497, A356280, A356281, A356282, A356283, A356289.
%K A356290 nonn
%O A356290 0,2
%A A356290 _Vaclav Kotesovec_, Aug 02 2022