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 A370889 #22 Mar 06 2024 11:28:17
%S A370889 1,1,2,9,72,735,9000,133035,2325120,46631025,1053108000,26484495345,
%T A370889 734652737280,22280390827695,733335188826240,26035824337798275,
%U A370889 991872319953715200,40360728513989909025,1747119524427614937600,80166580022376802179225
%N A370889 Expansion of e.g.f. (1/x) * Series_Reversion( x/(1 + x*exp(x^2/2)) ).
%H A370889 <a href="/index/Res#revert">Index entries for reversions of series</a>
%F A370889 a(n) = (n!/(n+1)) * Sum_{k=0..floor(n/2)} (n-2*k)^k * binomial(n+1,n-2*k)/(2^k * k!).
%F A370889 a(n) ~ (1 + 3*LambertW(1/3))^(n + 3/2) * n^(n-1) / (sqrt(1 + LambertW(1/3)) * 3^(3*n/2 + 2) * exp(n) * LambertW(1/3)^(3*(n+1)/2)). - _Vaclav Kotesovec_, Mar 06 2024
%o A370889 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(serreverse(x/(1+x*exp(x^2/2)))/x))
%o A370889 (PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)^k*binomial(n+1, n-2*k)/(2^k*k!))/(n+1);
%Y A370889 Cf. A161633, A370926.
%Y A370889 Cf. A365283.
%K A370889 nonn
%O A370889 0,3
%A A370889 _Seiichi Manyama_, Mar 05 2024