A031661 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 73.

12109, 66098, 109642, 110305, 163337, 306034, 387173, 388418, 390914, 393418, 394673, 481997, 484777, 596425, 709493, 719633, 723029, 841514, 845186, 850709, 852554, 854401, 1124441, 1137197, 1145741, 1298282, 1300561, 1457938, 1460353, 1489489

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Mathematica

cf73Q[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]]==73]; Select[Range[15*10^5], cf73Q] (* Harvey P. Dale, Oct 10 2017 *)

Crossrefs

Sequence in context: A008914 A257357 A070187 * A371952 A247403 A262635

Adjacent sequences: A031658 A031659 A031660 * A031662 A031663 A031664

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected and extended and definition clarified by Harvey P. Dale, Oct 10 2017

Status

approved