%I #12 Jul 11 2021 07:24:57

%S 949,1109,1261,1354,1361,1402,1721,1889,1921,2221,2561,2957,3229,3821,

%T 4021,4373,4481,4973,4985,5473,5545,5729,5765,5825,6065,6322,6458,

%U 6617,6730,6869,6925,6938,7109,7913,7985,8077,9034,9146,9178,9509,10061,10930

%N Numbers k such that the continued fraction for sqrt(k) has period 27.

%t cf27Q[n_]:=Module[{s=Sqrt[n]},If[IntegerQ[s],1,Length[ ContinuedFraction[ s][[2]]]] == 27]; Select[Range[11000],cf27Q] (* _Harvey P. Dale_, Jan 21 2019 *)

%K nonn

%O 1,1

%A _David W. Wilson_