A031568 - OEIS

%I #14 Jul 06 2024 16:08:44

%S 4902,4918,4934,4942,4946,4962,4978,4994,5006,5026,5058,5062,5074,

%T 5078,5086,5094,5102,5126,5142,5154,5158,5182,11028,11037,11073,11091,

%U 11121,11127,11157,11163,11166,11172,11181,11199,11217,11301,11337,11343,11361

%N Numbers k such 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 70.

%t cf70Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{1}, ContinuedFraction[ s][[2]]];len=Length[cf];EvenQ[len]&&cf[[len/2]] == 70]; Select[Range[11400],cf70Q] (* _Harvey P. Dale_, May 31 2021 *)

%K nonn

%O 1,1

%A _David W. Wilson_