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 A368964 #16 Jan 13 2024 10:45:21
%S A368964 1,3,15,94,660,4959,38995,316875,2639754,22423292,193484208,
%T A368964 1691190228,14942632450,133242614565,1197520200870,10836727044255,
%U A368964 98656011543816,902936341411170,8303218554134769,76679352910367832,710839322080978272,6612557820697157410
%N A368964 Expansion of (1/x) * Series_Reversion( x * (1-x-x^3)^3 ).
%H A368964 Seiichi Manyama, <a href="/A368964/b368964.txt">Table of n, a(n) for n = 0..1000</a>
%H A368964 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A368964 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(3*n+k+2,k) * binomial(4*n-2*k+2,n-3*k).
%o A368964 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x-x^3)^3)/x)
%o A368964 (PARI) a(n, s=3, t=3, u=0) = sum(k=0, n\s, binomial(t*(n+1)+k-1, k)*binomial((t+u+1)*(n+1)-(s-1)*k-2, n-s*k))/(n+1);
%Y A368964 Cf. A368963, A368972.
%K A368964 nonn
%O A368964 0,2
%A A368964 _Seiichi Manyama_, Jan 10 2024