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 A371386 #7 Mar 21 2024 09:19:26
%S A371386 1,7,89,1391,24209,450231,8759337,176071263,3627907745,76217773799,
%T A371386 1626477863801,35158334302927,768222871584817,16940297062253719,
%U A371386 376507441510456905,8425543117906277055,189683436162271517505,4293057440192560395207
%N A371386 Expansion of (1/x) * Series_Reversion( x * (1-4*x)^2 / (1-x) ).
%H A371386 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371386 a(n) = (1/(n+1)) * Sum_{k=0..n} 3^k * binomial(2*n+k+1,k) * binomial(2*n,n-k).
%o A371386 (PARI) my(N=20, x='x+O('x^N)); Vec(serreverse(x*(1-4*x)^2/(1-x))/x)
%o A371386 (PARI) a(n) = sum(k=0, n, 3^k*binomial(2*n+k+1, k)*binomial(2*n, n-k))/(n+1);
%Y A371386 Cf. A131763, A371387.
%Y A371386 Cf. A371364.
%K A371386 nonn
%O A371386 0,2
%A A371386 _Seiichi Manyama_, Mar 20 2024