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 A366052 #8 Sep 27 2023 10:06:56
%S A366052 1,2,7,31,154,819,4559,26226,154664,930040,5680920,35150493,219850505,
%T A366052 1387717660,8828668582,56553846890,364449091112,2361118198094,
%U A366052 15369247139879,100468188756849,659271433474584,4341140182940382,28675590236716905
%N A366052 Expansion of (1/x) * Series_Reversion( x*(1-x)^3/(1-x+x^3) ).
%F A366052 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(n+1,k) * binomial(3*n-2*k+1,n-3*k).
%o A366052 (PARI) a(n) = sum(k=0, n\3, binomial(n+1, k)*binomial(3*n-2*k+1, n-3*k))/(n+1);
%Y A366052 Cf. A049128, A114997, A366051, A366053.
%K A366052 nonn
%O A366052 0,2
%A A366052 _Seiichi Manyama_, Sep 27 2023