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 A334569 #21 May 03 2021 02:13:37
%S A334569 1,-1,0,0,6,-6,-24,-120,540,1764,2016,-68256,-147960,700920,11870496,
%T A334569 5245344,-330495984,-2602348560,6794046720,141179998464,619736321376,
%U A334569 -6025074044256,-66284988059520,-87481563442560,4660723755205056,34028147176271424,-98057302990861824
%N A334569 E.g.f.: exp(-(x + x^2/2 + x^3/3)).
%H A334569 Seiichi Manyama, <a href="/A334569/b334569.txt">Table of n, a(n) for n = 0..500</a>
%F A334569 a(0) = 1 and a(n) = - (n-1)! * Sum_{k=1..min(3,n)} a(n-k)/(n-k)!.
%F A334569 D-finite with recurrence a(n) +a(n-1) +(n-1)*a(n-2) +(n-1)*(n-2)*a(n-3)=0. - _R. J. Mathar_, May 07 2020
%t A334569 m = 25; Range[0, m]! * CoefficientList[Series[Exp[-(x + x^2/2 + x^3/3)], {x, 0, m}], x] (* _Amiram Eldar_, May 03 2021 *)
%o A334569 (PARI) N=40; x='x+O('x^N); Vec(serlaplace(exp(-x-x^2/2-x^3/3)))
%Y A334569 Column 3 of A334568.
%Y A334569 Cf. A057693, A334562.
%K A334569 sign
%O A334569 0,5
%A A334569 _Seiichi Manyama_, May 06 2020