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 A203811 #17 Jun 06 2021 10:56:10
%S A203811 1,2,6,12,60,20,140,280,2520,2520,27720,27720,360360,360360,72072,
%T A203811 144144,2450448,2450448,46558512,232792560,232792560,232792560,
%U A203811 5354228880,5354228880,26771144400,26771144400,80313433200,80313433200,2329089562800,2329089562800
%N A203811 Denominators of s(i) = s(i-1) - (1/i)*sign(s(i-1)) with s(1) = 1.
%C A203811 Numerators are given in A203810. The first 14 terms coincide with those of A002805.
%H A203811 Hugo Pfoertner, <a href="/A203811/b203811.txt">Table of n, a(n) for n = 1..200</a>
%e A203811 See A203810.
%t A203811 nxt[{n_,a_}]:={n+1,a-1/(n+1) Sign[a]}; NestList[nxt,{1,1},30][[All,2]]//Denominator (* _Harvey P. Dale_, Jun 06 2021 *)
%Y A203811 Cf. A002805, A203810 (numerators), A203812.
%K A203811 nonn,frac
%O A203811 1,2
%A A203811 _Hugo Pfoertner_ and _Rainer Rosenthal_, Jan 06 2012