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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.
0
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
OFFSET
1,1
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
KEYWORD
nonn
EXTENSIONS
Definition and terms corrected by Harvey P. Dale, Sep 27 2017
STATUS
approved