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 A354239 #73 Jun 08 2022 09:45:49
%S A354239 1,0,-1,-3,-9,-35,-195,-1477,-13839,-151335,-1877745,-26022491,
%T A354239 -398318481,-6674043961,-121496905803,-2387748622365,-50382638237343,
%U A354239 -1136006690370371,-27257495551671753,-693436310776781083,-18643640290958926785,-528196548501606911913
%N A354239 Expansion of e.g.f. (2 - exp(x))^(x/2).
%F A354239 a(0) = 1; a(n) = (-1/2) * Sum_{k=1..n} A052862(k) * binomial(n-1,k-1) * a(n-k).
%F A354239 a(n) ~ -n! / (Gamma(1 - log(2)/2) * 2^(1 - log(2)/2) * n^(log(2)/2 + 1) * log(2)^(n - log(2)/2 - 1)). - _Vaclav Kotesovec_, Jun 08 2022
%o A354239 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace((2-exp(x))^(x/2)))
%o A354239 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=-sum(j=1, i, j*sum(k=1, j-1, (k-1)!*stirling(j-1, k, 2))*binomial(i-1, j-1)*v[i-j+1])/2); v;
%Y A354239 Cf. A052862, A354412.
%K A354239 sign
%O A354239 0,4
%A A354239 _Seiichi Manyama_, May 26 2022