A031641 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 53.

17981, 35018, 35393, 57202, 58162, 58645, 85385, 161026, 163441, 209138, 210053, 254377, 258425, 260461, 262505, 372629, 376298, 384929, 441521, 444181, 446849, 448186, 450866, 454901, 516253, 522013, 530713, 596825, 603017, 606125, 609241

Offset

1,1

Links

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

Mathematica

cf53Q[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]] == 53]; Select[Range[610000], cf53Q] (* Harvey P. Dale, Jul 14 2017 *)

Crossrefs

Sequence in context: A345869 A345585 A345842 * A106769 A224571 A251832

Adjacent sequences: A031638 A031639 A031640 * A031642 A031643 A031644

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected and extended by Harvey P. Dale, Jul 14 2017

Status

approved