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A031423 Numbers n such that continued fraction for sqrt(n) has odd period and a pair of central terms both equal to 10. 20
701, 1418, 1493, 2197, 2290, 3257, 4793, 6154, 6466, 8389, 8753, 9577, 9965, 10765, 11257, 11677, 12541, 14218, 14929, 15413, 15658, 16001, 16501, 17009, 17786, 18049, 18314, 18581, 19121, 21577, 22157, 22745, 24557, 24677, 25805, 26561, 27530, 28517 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000 [shifted by Georg Fischer, Jun 26 2019]

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]] == 10 && c[[2, (len + 1)/2 - 1]] == 10, AppendTo[t, n]]]]; t (* T. D. Noe, Apr 04 2014; corrected by Georg Fischer, Jun 23 2019 *)

CROSSREFS

Cf. A031404-A031422.

Sequence in context: A093235 A223351 A180469 * A140433 A316969 A303689

Adjacent sequences:  A031420 A031421 A031422 * A031424 A031425 A031426

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

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

a(1) = 26 removed by Georg Fischer, Jun 23 2019

STATUS

approved

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Last modified September 28 12:34 EDT 2020. Contains 337393 sequences. (Running on oeis4.)