A031422 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted then there are a pair of central terms both equal to 9.

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

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.

Subsequence of A003814.

Sequence in context: A020370 A325089 A050202 * A359638 A078966 A255024

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