%I #7 Aug 02 2024 11:13:46
%S 1381,1501,1588,1609,2137,2293,2469,2473,2476,2481,2497,2529,2564,
%T 2721,2909,3013,3073,3076,3117,3119,3149,3241,3307,3326,3343,3539,
%U 3583,3748,3847,3884,3994,4039,4078,4117,4269,4349,4456,4459,4492,4581,4612,4654
%N Period of continued fraction for sqrt(n) contains exactly 28 ones.
%t cf28Q[n_]:=With[{s=Sqrt[n]},If[IntegerQ[s],1,Count[ContinuedFraction[s][[2]],1]]==28]; Select[ Range[ 5000],cf28Q] (* _Harvey P. Dale_, Aug 02 2024 *)
%K nonn
%O 1,1
%A _David W. Wilson_