%I #12 Mar 14 2015 21:28:53
%S 7,32,75,88,136,215,279,280,312,403,427,560,711,736,851,880,923,1007,
%T 1067,1272,1311,1363,1431,1495,1736,1855,1887,1955,1976,1995,2128,
%U 2159,2184,2272,2511,2567,2640,2728,2880,3055,3211,3560,3751,3811,3927,3984
%N Period of continued fraction for sqrt(n) contains exactly three 1's.
%D Kenneth H. Rosen, Elementary Number Theory and Its Applications, Addison-Wesley, 1984, p. 426 (but beware of errors!).
%t Select[ Range@ 1900, !IntegerQ[ Sqrt@ #] && Count[ ContinuedFraction[ Sqrt@ #][[2]], 1] == 3 &] (* _Robert G. Wilson v_, Jul 03 2011 *)
%K nonn
%O 1,1
%A _Clark Kimberling_
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