A020388 - OEIS

%I #12 Jul 11 2021 07:23:54

%S 1021,1597,2617,2746,2861,3041,3881,4049,6469,6737,8497,9677,9970,

%T 10049,10181,11114,12829,12973,14426,14842,15145,16141,16277,18265,

%U 19357,19385,20605,21002,22738,24842,26002,26489,26938,27733,28922,29362,29789,30025

%N Numbers k such that the continued fraction for sqrt(k) has period 49.

%t cf49Q[n_]:=Module[{s=Sqrt[n]},If[IntegerQ[s],1,Length[ ContinuedFraction[ s] [[2]]]]==49]; Select[Range[31000],cf49Q] (* _Harvey P. Dale_, Mar 31 2018 *)

%K nonn

%O 1,1

%A _David W. Wilson_