A031552 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 54.

2918, 2942, 2946, 2962, 2966, 2974, 2978, 2994, 2998, 3022, 3046, 3058, 3062, 3086, 3106, 3118, 3126, 3134, 6564, 6573, 6591, 6609, 6621, 6636, 6663, 6693, 6702, 6717, 6729, 6753, 6771, 6774, 6789, 6801, 6807, 6852, 6861, 6879, 6924, 6933, 6951, 7017

Offset

1,1

Links

Table of n, a(n) for n=1..42.

Mathematica

cf54Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[s] [[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]]==54]; Select[Range[7100], cf54Q] (* Harvey P. Dale, May 13 2022 *)

Crossrefs

Sequence in context: A081634 A358879 A054830 * A205253 A251353 A036260

Adjacent sequences: A031549 A031550 A031551 * A031553 A031554 A031555

Keyword

nonn

Author

David W. Wilson

Extensions

Definition clarified by Harvey P. Dale, May 13 2022

Status

approved