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 A370927 #14 Mar 06 2024 08:00:05
%S A370927 1,1,4,36,480,8460,187200,4998000,156387840,5614313040,227520921600,
%T A370927 10275211679040,511772590264320,27870149349282240,1647541857684602880,
%U A370927 105073768465758892800,7191330561736409088000,525746801445336504633600
%N A370927 Expansion of e.g.f. (1/x) * Series_Reversion( x*(1 - x*exp(x^2)) ).
%H A370927 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A370927 a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} (n-2*k)^k * (2*n-2*k)!/(k! * (n-2*k)!).
%o A370927 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(serreverse(x*(1-x*exp(x^2)))/x))
%o A370927 (PARI) a(n) = sum(k=0, n\2, (n-2*k)^k*(2*n-2*k)!/(k!*(n-2*k)!))/(n+1);
%Y A370927 Cf. A213644, A370928.
%K A370927 nonn
%O A370927 0,3
%A A370927 _Seiichi Manyama_, Mar 06 2024