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 A068589 #15 May 07 2020 06:16:06
%S A068589 1,4,36,144,3600,1200,58800,235200,6350400,6350400,768398400,
%T A068589 768398400,129859329600,129859329600,129859329600,519437318400,
%U A068589 150117385017600,50039128339200,18064125330451200,18064125330451200,54192375991353600
%N A068589 Denominator(Sum_{i=1..n} 1/i^3)/denominator(Sum_{i=1..n} 1/i).
%C A068589 For n = 1 to n = 19, we have a(n) = A334580(n), but a(20) = 18064125330451200 <> 3612825066090240 = A334580(20). - _Petros Hadjicostas_, May 06 2020
%F A068589 a(n) = A007409(n)/A002805(n).
%p A068589 a := proc(n) local i: denom(add(1/i^3, i = 1 .. n))/denom(add(1/i, i = 1 .. n)): end proc:
%p A068589 seq(a(n), n=1..30); # _Petros Hadjicostas_, May 06 2020
%o A068589 (PARI) a(n) = denominator(sum(k=1, n, 1/k^3)/sum(k=1, n, 1/k)); \\ _Michel Marcus_, May 07 2020
%Y A068589 Cf. A002805, A007409, A119682, A334580.
%K A068589 easy,nonn
%O A068589 1,2
%A A068589 _Benoit Cloitre_, Mar 27 2002