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 A369014 #17 Jan 14 2024 08:54:09
%S A369014 1,0,0,3,3,3,36,78,129,685,2043,4554,17233,57279,153045,509848,
%T A369014 1724739,5117643,16445555,55165536,173225715,555899673,1847495415,
%U A369014 5971507824,19333284247,63975307425,209807070669,685973054145,2269660792842,7501194321663,24725092907853
%N A369014 Expansion of (1/x) * Series_Reversion( x * (1-x^3/(1-x))^3 ).
%H A369014 Seiichi Manyama, <a href="/A369014/b369014.txt">Table of n, a(n) for n = 0..1000</a>
%H A369014 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369014 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(3*n+k+2,k) * binomial(n-2*k-1,n-3*k).
%o A369014 (PARI) my(N=40, x='x+O('x^N)); Vec(serreverse(x*(1-x^3/(1-x))^3)/x)
%o A369014 (PARI) a(n, s=3, t=3, u=-3) = 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 A369014 Cf. A369012, A369013.
%Y A369014 Cf. A054514, A369011.
%K A369014 nonn
%O A369014 0,4
%A A369014 _Seiichi Manyama_, Jan 11 2024