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 A371363 #11 Mar 20 2024 09:35:36
%S A371363 1,7,85,1261,20788,365845,6731758,127938625,2491921516,49480794460,
%T A371363 997897366717,20384025765619,420869454302620,8769197604091246,
%U A371363 184151509243984300,3893585866824069577,82817275938125471548,1770880435886367151060
%N A371363 Expansion of (1/x) * Series_Reversion( x * (1-3*x)^3 / (1-2*x) ).
%H A371363 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371363 a(n) = (1/(n+1)) * Sum_{k=0..n} 2^(n-k) * binomial(3*n+k+2,k) * binomial(3*n+1,n-k).
%o A371363 (PARI) my(N=20, x='x+O('x^N)); Vec(serreverse(x*(1-3*x)^3/(1-2*x))/x)
%o A371363 (PARI) a(n) = sum(k=0, n, 2^(n-k)*binomial(3*n+k+2, k)*binomial(3*n+1, n-k))/(n+1);
%Y A371363 Cf. A007564, A371362.
%Y A371363 Cf. A369023, A371365.
%K A371363 nonn
%O A371363 0,2
%A A371363 _Seiichi Manyama_, Mar 19 2024