A031781 - OEIS

A031781

Period of continued fraction for sqrt(n) contains exactly 13 ones.

1219, 1591, 2071, 2107, 3375, 3655, 4175, 4399, 4671, 4847, 4888, 4891, 5319, 5395, 6208, 7067, 7144, 7515, 11800, 12328, 12875, 12947, 13144, 13199, 13511, 14027, 14319, 15151, 15272, 16120, 16403, 17331, 17759, 17936, 18483, 19327, 19527, 19691

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OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..650

MATHEMATICA

cf13Q[n_]:=Module[{s=Sqrt[n]}, If[IntegerQ[s], 1, Count[ ContinuedFraction[ s][[2]], 1]]==13]; Select[Range[20000], cf13Q] (* Harvey P. Dale, Jun 16 2017 *)

CROSSREFS

Sequence in context: A300408 A252600 A293479 * A069400 A233660 A015279

Adjacent sequences: A031778 A031779 A031780 * A031782 A031783 A031784

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved