%I #12 Aug 17 2021 23:48:27
%S 8102,8114,8126,8158,8166,8182,8194,8198,8222,8254,8258,8262,8278,
%T 8302,8306,8318,8338,8342,8402,8406,8414,8422,8434,8438,8454,8462,
%U 18228,18237,18273,18291,18294,18366,18372,18393,18399,18417,18429,18453,18489,18507
%N that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 90.
%t cf90Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{1}, ContinuedFraction[ s][[2]]];len=Length[cf];EvenQ[len]&&cf[[len/2]]==90]; Select[Range[20000],cf90Q] (* _Harvey P. Dale_, Mar 30 2020 *)
%K nonn
%O 1,1
%A _David W. Wilson_
