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 A369481 #11 Jan 24 2024 05:55:31
%S A369481 1,2,5,15,51,187,718,2844,11530,47612,199576,847013,3632468,15717041,
%T A369481 68527255,300780438,1327939406,5893299392,26275243626,117635107818,
%U A369481 528631769323,2383660351991,10781500113896,48903885040638,222400899237943,1013841791472632
%N A369481 Expansion of (1/x) * Series_Reversion( x / ((1+x) * (1+x+x^3)) ).
%H A369481 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A369481 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} binomial(n+1,k) * binomial(2*n-k+2,n-3*k).
%o A369481 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x/((1+x)*(1+x+x^3)))/x)
%o A369481 (PARI) a(n, s=3, t=1, u=1) = sum(k=0, n\s, binomial(t*(n+1), k)*binomial((t+u)*(n+1)-k, n-s*k))/(n+1);
%Y A369481 Cf. A071879, A369482.
%K A369481 nonn
%O A369481 0,2
%A A369481 _Seiichi Manyama_, Jan 23 2024