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 A371392 #12 Mar 21 2024 09:19:52
%S A371392 1,7,68,769,9492,124014,1686120,23610565,338200148,4932348226,
%T A371392 72993007672,1093371638954,16545598769416,252567107648604,
%U A371392 3884497559034192,60136704175071789,936373570430169300,14654788984834217850,230405413840884827160,3637362857723455772670
%N A371392 Expansion of (1/x) * Series_Reversion( x * (1-x) / (1+2*x)^3 ).
%H A371392 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A371392 a(n) = (1/(n+1)) * Sum_{k=0..n} 2^k * binomial(3*(n+1),k) * binomial(2*n-k,n-k).
%o A371392 (PARI) my(N=30, x='x+O('x^N)); Vec(serreverse(x*(1-x)/(1+2*x)^3)/x)
%o A371392 (PARI) a(n) = sum(k=0, n, 2^k*binomial(3*(n+1), k)*binomial(2*n-k, n-k))/(n+1);
%Y A371392 Cf. A047891, A371391.
%Y A371392 Cf. A113207.
%K A371392 nonn
%O A371392 0,2
%A A371392 _Seiichi Manyama_, Mar 21 2024