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 A362088 #7 Apr 08 2023 11:06:40
%S A362088 1,1,9,55,369,2526,17577,123810,879921,6297643,45325764,327720471,
%T A362088 2378598885,17319785588,126463925310,925620561780,6789081127137,
%U A362088 49887667836693,367189338574827,2706613194698783,19977334121704344,147628150691297100
%N A362088 a(n) = Sum_{k=0..n} (-1)^k * binomial(-n,k) * binomial(3*k,n-k).
%F A362088 a(n) = Sum_{k=0..n} binomial(n+k-1,k) * binomial(3*k,n-k).
%F A362088 a(n) = [x^n] 1/(1 - x*(1+x)^3)^n.
%o A362088 (PARI) a(n) = sum(k=0, n, binomial(n+k-1, k)*binomial(3*k, n-k));
%Y A362088 Column k=3 of A362078.
%Y A362088 Cf. A362085.
%K A362088 nonn
%O A362088 0,3
%A A362088 _Seiichi Manyama_, Apr 08 2023