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 A361548 #13 Nov 03 2024 18:03:58
%S A361548 1,1,4,20,126,966,8656,88544,1016380,12920156,179996816,2725070096,
%T A361548 44521522024,780344770440,14599772973696,290311643773376,
%U A361548 6112190642062096,135798496839920144,3174483084427144000,77872118431269176896,1999809157085214044896
%N A361548 Expansion of e.g.f. exp((x + x^2/2 + x^3/6)/(1-x)).
%F A361548 a(n) = (2*n-1) * a(n-1) - (n-1)*(n-3) * a(n-2) - 2*binomial(n-1,3) * a(n-4) for n > 3.
%t A361548 With[{nn=20},CoefficientList[Series[Exp[(x+x^2/2+x^3/6)/(1-x)],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Nov 03 2024 *)
%o A361548 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp((x+x^2/2+x^3/6)/(1-x))))
%Y A361548 Cf. A361532, A361557, A361558.
%K A361548 nonn
%O A361548 0,3
%A A361548 _Seiichi Manyama_, Mar 15 2023