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 A020439 #18 Aug 25 2025 02:15:20
%S A020439 2629,3646,4924,5692,5833,5836,6172,6703,6801,7389,7438,8158,8287,
%T A020439 8551,8654,9103,10041,10079,10096,10629,10936,11038,11068,11116,11335,
%U A020439 11383,11519,11824,11863,11995,12016,12044,12494,12751,12811,12895,13372,13569
%N A020439 Numbers k such that the continued fraction for sqrt(k) has period 100.
%H A020439 Amiram Eldar, <a href="/A020439/b020439.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)
%t A020439 nn=15000;With[{nonsq=Complement[Range[nn],Range[ Floor[Sqrt[nn]]]^2]}, Select[ nonsq,Length[ ContinuedFraction[Sqrt[#]][[2]]]==100&]] (* _Harvey P. Dale_, May 22 2012 *)
%Y A020439 Cf. A003285.
%K A020439 nonn,changed
%O A020439 1,1
%A A020439 _David W. Wilson_