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 A369623 #9 Jan 28 2024 09:19:35
%S A369623 1,3,15,92,624,4509,34033,265164,2116560,17219068,142252608,
%T A369623 1190173956,10064038469,85873044573,738446318232,6393218956733,
%U A369623 55680130965252,487488352916496,4288083926110045,37878037865662422,335859658273133355,2988274511990407436
%N A369623 Expansion of (1/x) * Series_Reversion( x / (1/(1-x)^3 + x^3) ).
%H A369623 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369623 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(n+1,k) * binomial(4*n-6*k+2,n-3*k).
%o A369623 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/(1/(1-x)^3+x^3))/x)
%o A369623 (PARI) a(n) = sum(k=0, n\3, binomial(n+1, k)*binomial(4*n-6*k+2, n-3*k))/(n+1);
%Y A369623 Cf. A369621, A369622.
%Y A369623 Cf. A369600.
%K A369623 nonn
%O A369623 0,2
%A A369623 _Seiichi Manyama_, Jan 27 2024