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A031514 that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 16. 0

%I

%S 258,262,278,302,322,579,597,633,651,654,669,681,687,717,726,1028,

%T 1052,1060,1068,1076,1084,1108,1116,1124,1132,1148,1164,1172,1212,

%U 1228,1244,1252,1268,1276,1292,1605,1630,1645,1655,1670,1795,1805,1830,1895,1905

%N that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 16.

%t cf16Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{1}, ContinuedFraction[ s][[2]]];len=Length[cf];EvenQ[len] && cf[[len/2]] == 16]; Select[Range[2000],cf16Q] (* _Harvey P. Dale_, Mar 04 2018 *)

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified January 24 21:49 EST 2022. Contains 350565 sequences. (Running on oeis4.)