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 A380014 #9 Jan 23 2025 04:53:46
%S A380014 1,2,10,88,1084,17176,332824,7623904,201540112,6038820640,
%T A380014 202246657696,7486877795200,303561658686400,13378863292503424,
%U A380014 636833910410881408,32559375816074384896,1779494669204225605888,103532173699456380625408,6388705590982575700625920
%N A380014 Expansion of e.g.f. 1/sqrt(exp(-2*x) - 2*x).
%F A380014 a(n) = n! * Sum_{k=0..n} (-2)^k * (2*k+1)^(n-k) * binomial(-1/2,k)/(n-k)!.
%F A380014 a(n) ~ 2^(n + 1/2) * n^n / (sqrt(1 + LambertW(1)) * LambertW(1)^(n + 1/2) * exp(n)). - _Vaclav Kotesovec_, Jan 23 2025
%o A380014 (PARI) a(n) = n!*sum(k=0, n, (-2)^k*(2*k+1)^(n-k)*binomial(-1/2, k)/(n-k)!);
%Y A380014 Cf. A072597, A380016, A380018.
%K A380014 nonn
%O A380014 0,2
%A A380014 _Seiichi Manyama_, Jan 09 2025