%I #14 Aug 17 2021 23:48:27
%S 963,967,971,983,991,1003,1019,1031,1039,1051,1059,1063,1087,3848,
%T 3880,3904,3936,3944,4000,4040,4072,4168,4192,4256,4264,4288,4320,
%U 4328,4352,8655,8727,8787,8871,8943,9003,9147,9303,9375,9663,9795,15384,15448
%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 31.
%t epct31Q[n_]:=Module[{cf=ContinuedFraction[Sqrt[n]],cf2},If[Length[cf] ==1, cf2={1},cf2=cf[[2]]];EvenQ[Length[ cf2]] && cf2[[Length[cf2]/2]] == 31]; Select[ Range[16000],epct31Q] (* _Harvey P. Dale_, Dec 07 2012 *)
%K nonn
%O 1,1
%A _David W. Wilson_
