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 A366050 #8 Sep 27 2023 10:07:03
%S A366050 1,3,16,104,750,5769,46373,384885,3273118,28372354,249762585,
%T A366050 2226782078,20065651123,182457467898,1672073116401,15427427247088,
%U A366050 143191280370438,1336062703751262,12524930325385008,117910257665608080,1114233543986585741
%N A366050 Expansion of (1/x) * Series_Reversion( x*(1-x)^4/(1-x+x^2) ).
%F A366050 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} binomial(n+1,k) * binomial(4*n-k+2,n-2*k).
%o A366050 (PARI) a(n) = sum(k=0, n\2, binomial(n+1, k)*binomial(4*n-k+2, n-2*k))/(n+1);
%Y A366050 Cf. A005043, A109081, A366049.
%K A366050 nonn
%O A366050 0,2
%A A366050 _Seiichi Manyama_, Sep 27 2023