%I #7 Jun 16 2017 11:34:15

%S 1219,1591,2071,2107,3375,3655,4175,4399,4671,4847,4888,4891,5319,

%T 5395,6208,7067,7144,7515,11800,12328,12875,12947,13144,13199,13511,

%U 14027,14319,15151,15272,16120,16403,17331,17759,17936,18483,19327,19527,19691

%N Period of continued fraction for sqrt(n) contains exactly 13 ones.

%H Harvey P. Dale, <a href="/A031781/b031781.txt">Table of n, a(n) for n = 1..650</a>

%t cf13Q[n_]:=Module[{s=Sqrt[n]},If[IntegerQ[s],1,Count[ ContinuedFraction[ s][[2]],1]]==13]; Select[Range[20000],cf13Q] (* _Harvey P. Dale_, Jun 16 2017 *)

%K nonn

%O 1,1

%A _David W. Wilson_