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 A371366 #12 Mar 20 2024 09:39:36
%S A371366 1,6,71,1046,17231,303876,5611556,107128046,2097177071,41870595806,
%T A371366 849284396751,17451906690856,362539208779396,7601087206512096,
%U A371366 160635649725455256,3418231465333316126,73178876192536066031,1575035438677302619746
%N A371366 Expansion of (1/x) * Series_Reversion( x * (1-5*x)^2 / (1-4*x) ).
%H A371366 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371366 a(n) = (1/(n+1)) * Sum_{k=0..n} 4^(n-k) * binomial(2*n+k+1,k) * binomial(2*n,n-k).
%o A371366 (PARI) my(N=20, x='x+O('x^N)); Vec(serreverse(x*(1-5*x)^2/(1-4*x))/x)
%o A371366 (PARI) a(n) = sum(k=0, n, 4^(n-k)*binomial(2*n+k+1, k)*binomial(2*n, n-k))/(n+1);
%Y A371366 Cf. A078009.
%K A371366 nonn
%O A371366 0,2
%A A371366 _Seiichi Manyama_, Mar 19 2024