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 A160622 #11 Sep 08 2022 08:45:45
%S A160622 1,1,2,3,8,15,144,420,5760,4536,403200,1995840,6220800,259459200,
%T A160622 1341204480,46702656000,1394852659200,11115232128000,376610217984000,
%U A160622 96543730483200,128047474114560000,1277273554292736000
%N A160622 Denominator of Laguerre(n, 1).
%H A160622 G. C. Greubel, <a href="/A160622/b160622.txt">Table of n, a(n) for n = 0..450</a>
%F A160622 Denominators of coefficients in expansion of exp(-x/(1 - x))/(1 - x). - _Ilya Gutkovskiy_, Aug 29 2018
%e A160622 1, 0, -1/2, -2/3, -5/8, -7/15, -37/144, -17/420, 887/5760, 1405/4536, 168919/403200, 958271/1995840, ... = A160621/A160622.
%t A160622 Denominator[Table[LaguerreL[n,1], {n, 0, 50}]] (* _G. C. Greubel_, May 06 2018 *)
%o A160622 (PARI) for(n=0,30, print1(denominator(sum(k=0,n, binomial(n,k)*((-1)^k/k!))), ", ")) \\ _G. C. Greubel_, May 06 2018
%o A160622 (Magma) [Denominator((&+[Binomial(n,k)*((-1)^k/Factorial(k)): k in [0..n]])): n in [0..30]]; // _G. C. Greubel_, May 06 2018
%Y A160622 For numerators see A160621.
%Y A160622 Cf. A009940.
%K A160622 nonn,frac
%O A160622 0,3
%A A160622 _N. J. A. Sloane_, Nov 14 2009