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 A068576 #18 Feb 17 2021 04:05:21
%S A068576 28,56,153,172,173,175,176,177,178,180,181,344,351,352,353,354,356,
%T A068576 357,361,362,363,365,366,367,368,370,371,373,374,375,383,386,391,393,
%U A068576 394,395,396,397,400,405,408,425,428,640,752,848,849,850,851,852,853,854
%N A068576 Numbers k such that Sum_{j=1..k} mu(j)^2 = floor(6*k/Pi^2).
%H A068576 Amiram Eldar, <a href="/A068576/b068576.txt">Table of n, a(n) for n = 1..10000</a>
%t A068576 seq[max_] := Flatten @ Position[Accumulate @ Array[Boole @ SquareFreeQ[#] &, max] - Floor[6*Range[max]/Pi^2], 0]; seq[1000] (* _Amiram Eldar_, Feb 17 2021 *)
%o A068576 (PARI) isok(k) = sum(j=1, k, moebius(j)^2) == 6*k\Pi^2; \\ _Michel Marcus_, Feb 15 2021
%Y A068576 Cf. A008683, A013928, A059956.
%K A068576 easy,nonn
%O A068576 1,1
%A A068576 _Benoit Cloitre_, Mar 26 2002