A031654 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 66.

1090, 10009, 27581, 89482, 90682, 134077, 135545, 185069, 186793, 246241, 316133, 321778, 487645, 581173, 582698, 585754, 590353, 593429, 682901, 686209, 687866, 691186, 696181, 699521, 796393, 814333, 930137, 937865, 941741, 1049537, 1061861

Offset

1,1

Links

Table of n, a(n) for n=1..31.

Mathematica

op66Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[(len+1)/2]] == 66]; Select[Range[11*10^5], op66Q] (* Harvey P. Dale, Mar 14 2016 *)

Crossrefs

Sequence in context: A169977 A345408 A031744 * A031531 A161118 A031711

Adjacent sequences: A031651 A031652 A031653 * A031655 A031656 A031657

Keyword

nonn

Author

David W. Wilson

Extensions

Terms corrected and definition corrected by Harvey P. Dale, Mar 14 2016

Status

approved