A031558 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 60.

3602, 3618, 3622, 3638, 3646, 3662, 3686, 3694, 3698, 3702, 3714, 3734, 3742, 3746, 3758, 3762, 3778, 3798, 3814, 3826, 3842, 8103, 8121, 8133, 8148, 8157, 8193, 8214, 8247, 8286, 8292, 8301, 8337, 8349, 8373, 8391, 8409, 8436, 8457, 8499, 8502, 8529

Offset

1,1

Links

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

Mathematica

cf60Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]]==60]; Select[ Range[ 9000], cf60Q] (* Harvey P. Dale, Jan 13 2025 *)

Crossrefs

Sequence in context: A003838 A296907 A157861 * A045817 A107538 A270260

Adjacent sequences: A031555 A031556 A031557 * A031559 A031560 A031561

Keyword

nonn

Author

David W. Wilson

Status

approved