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 A068584 #18 Feb 18 2021 02:35:06
%S A068584 1,2,3,4,5,9,15,16,17,28,29,30,31,32,49,91,92,93,94,95,96,97,98,99,
%T A068584 125,126,127,128,129,130,131,132,133,134,135,243,244,245,246,247,248,
%U A068584 249,968,969,970,971,972,973,974,975,976,977,978,979,980,981,982,983,984
%N A068584 Numbers k such that the denominator of (Sum_{j=1..k} 1/j)^2 equals the denominator of Sum_{j=1..k} 1/j^2.
%H A068584 Amiram Eldar, <a href="/A068584/b068584.txt">Table of n, a(n) for n = 1..10000</a>
%F A068584 Numbers k such that A002805(k)^2 = A007407(k).
%t A068584 s = {}; sum1 = sum2 = 0; Do[sum1 += 1/j; sum2 += 1/j^2; If[Denominator[sum1^2] == Denominator[sum2], AppendTo[s, j]], {j, 1, 1000}]; s (* _Amiram Eldar_, Feb 18 2021 *)
%o A068584 (PARI) isok(k) = denominator(sum(j=1, k, 1/j)^2) == denominator(sum(j=1, k, 1/j^2)); \\ _Michel Marcus_, Feb 15 2021
%Y A068584 Cf. A002805, A007407.
%K A068584 easy,nonn
%O A068584 1,2
%A A068584 _Benoit Cloitre_, Mar 27 2002