A031604 - OEIS

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A031604

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 16.

65, 1789, 3413, 5410, 5557, 5857, 8221, 11833, 12269, 14866, 15601, 19058, 19333, 19889, 24077, 24697, 25325, 30025, 31417, 35498, 35873, 36629, 37778, 41429, 42241, 43889, 45146, 55597, 56537, 57485, 58441, 60377, 62962, 63962, 64465, 67010, 70258

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..37.

MATHEMATICA

cf16Q[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]] == 16]; Select[Range[71000], cf16Q] (* Harvey P. Dale, Sep 27 2017 *)

CROSSREFS

Sequence in context: A221501 A183271 A197088 * A002502 A333118 A095027

Adjacent sequences: A031601 A031602 A031603 * A031605 A031606 A031607

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Definition and terms corrected by Harvey P. Dale, Sep 27 2017

STATUS

approved