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A031422 Numbers n such that continued fraction for sqrt(n) has odd period and a pair of central terms both equal to 9. 2
601, 1073, 1930, 2017, 2621, 2825, 3037, 3533, 3769, 4013, 4714, 5701, 6218, 6373, 6689, 7013, 7757, 8461, 8825, 9197, 9277, 12629, 13394, 13621, 14081, 14549, 15613, 15754, 18265, 18797, 20005, 20282, 20441, 21410, 22277, 22993, 23762, 24065, 24370, 25114 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

MATHEMATICA

n = 1; t = {}; While[Length[t] < 50, n++; If[! IntegerQ[Sqrt[n]], c = ContinuedFraction[Sqrt[n]]; len = Length[c[[2]]]; If[OddQ[len] && c[[2, (len + 1)/2]] == 9, AppendTo[t, n]]]]; t (* T. D. Noe, Apr 04 2014 *)

CROSSREFS

Cf. A031404-A031423.

Sequence in context: A020370 A325089 A050202 * A078966 A255024 A283923

Adjacent sequences:  A031419 A031420 A031421 * A031423 A031424 A031425

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

a(1) removed by T. D. Noe, Apr 04 2014

STATUS

approved

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Last modified June 17 05:50 EDT 2021. Contains 345080 sequences. (Running on oeis4.)