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 A031668 #16 Jul 24 2022 15:48:47
%S A031668 40829,132577,195485,197257,362629,365041,466778,473633,584057,587117,
%T A031668 590185,850613,852458,1002626,1006634,1014674,1016689,1018706,1024769,
%U A031668 1184473,1188829,1351085,1360397,1365065,1374425,1541042,1548497
%N A031668 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 80.
%t A031668 cf80Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{0,0},ContinuedFraction[s][[2]]];len=Length[cf];OddQ[len]&&cf[[Floor[len/2]]]==cf[[Ceiling[len/2]]]==80]; Select[Range[155*10^4],cf80Q] (* _Harvey P. Dale_, Jul 24 2022 *)
%Y A031668 Subsequence of A003814.
%K A031668 nonn
%O A031668 1,1
%A A031668 _David W. Wilson_
%E A031668 First term 6401 removed by _Georg Fischer_, Jun 16 2019