A031584 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 86.

7398, 7414, 7438, 7446, 7454, 7458, 7478, 7506, 7534, 7542, 7554, 7558, 7586, 7606, 7634, 7646, 7654, 7666, 7682, 7694, 7698, 7702, 7718, 7726, 7734, 7742, 16644, 16653, 16671, 16689, 16743, 16773, 16782, 16788, 16809, 16833, 16869, 16917, 16941, 16953

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Mathematica

cf86Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]] == 86]; Select[ Range[17000], cf86Q] (* Harvey P. Dale, Jan 15 2019 *)

Crossrefs

Sequence in context: A206202 A364182 A034279 * A237311 A023940 A116195

Adjacent sequences: A031581 A031582 A031583 * A031585 A031586 A031587

Keyword

nonn

Author

David W. Wilson

Status

approved