%I #8 Jun 06 2021 18:17:19
%S 2,5,6,10,11,12,17,18,20,26,27,28,30,37,38,39,40,41,42,50,51,55,56,65,
%T 66,68,72,82,83,84,87,89,90,101,102,104,105,110,122,123,126,128,130,
%U 131,132,145,146,147,148,150,152,155,156,170,171,174,177,180,182,197,198,200,203
%N Period of continued fraction for sqrt(n) contains no 1's.
%D Kenneth H. Rosen, Elementary Number Theory and Its Applications, Addison-Wesley, 1984, page 426 (but beware of errors!).
%H T. D. Noe, <a href="/A013647/b013647.txt">Table of n, a(n) for n = 1..1000</a>
%t cf1Q[n_]:=Module[{s=Sqrt[n]},If[IntegerQ[s],False,FreeQ[ ContinuedFraction[ s][[2]],1]]]; Select[Range[250],cf1Q] (* _Harvey P. Dale_, Jun 06 2021 *)
%K nonn
%O 1,1
%A _Clark Kimberling_