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A031616 Numbers n such that continued fraction for sqrt(n) has odd period and central terms 28. 0
5209, 16210, 16465, 16981, 24457, 35513, 45169, 46021, 58853, 59338, 60314, 72185, 74345, 75437, 92857, 106154, 107458, 108113, 110753, 123826, 124529, 125941, 127361, 128074, 128789, 131669, 151273, 168941, 170585, 172237, 173897 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

cf28Q[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]] == 28]; Rest[Select[Range[174000], cf28Q]] (* Harvey P. Dale, Jun 24 2020 *)

CROSSREFS

Sequence in context: A109159 A231113 A289514 * A067224 A204139 A237408

Adjacent sequences:  A031613 A031614 A031615 * A031617 A031618 A031619

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

First term 785 removed by Georg Fischer, Jun 16 2019

STATUS

approved

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Last modified September 22 22:24 EDT 2020. Contains 337291 sequences. (Running on oeis4.)