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 A371380 #16 Mar 21 2024 09:19:07
%S A371380 1,5,46,521,6574,88658,1250920,18236849,272544886,4153080950,
%T A371380 64284022516,1007929418570,15974993572732,255522850658564,
%U A371380 4119461259700060,66869059171095809,1091990982773631910,17927521032225339854,295717190725184361364,4898634803627227516238
%N A371380 Expansion of (1/x) * Series_Reversion( x * (1-3*x)^2 / (1-x) ).
%H A371380 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371380 a(n) = (1/(n+1)) * Sum_{k=0..n} 2^k * binomial(2*n+k+1,k) * binomial(2*n,n-k).
%o A371380 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-3*x)^2/(1-x))/x)
%o A371380 (PARI) a(n) = sum(k=0, n, 2^k*binomial(2*n+k+1, k)*binomial(2*n, n-k))/(n+1);
%Y A371380 Cf. A107841, A371385.
%Y A371380 Cf. A371362.
%K A371380 nonn
%O A371380 0,2
%A A371380 _Seiichi Manyama_, Mar 20 2024