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 A366056 #8 Sep 27 2023 10:06:42
%S A366056 1,3,15,91,613,4408,33143,257400,2048825,16625940,137033316,
%T A366056 1144010387,9653706723,82208879366,705587243802,6097408839400,
%U A366056 53007770199641,463269048213536,4067950092964440,35871913838983980,317533385082542404,2820492099258807887
%N A366056 Expansion of (1/x) * Series_Reversion( x*(1-x)^4/(1-x+x^4) ).
%F A366056 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/4)} binomial(n+1,k) * binomial(4*n-3*k+2,n-4*k).
%o A366056 (PARI) a(n) = sum(k=0, n\4, binomial(n+1, k)*binomial(4*n-3*k+2, n-4*k))/(n+1);
%Y A366056 Cf. A215341, A366054, A366055.
%K A366056 nonn
%O A366056 0,2
%A A366056 _Seiichi Manyama_, Sep 27 2023