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 A031781 Period of continued fraction for sqrt(n) contains exactly 13 ones. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified June 21 12:50 EDT 2024. Contains 373544 sequences. (Running on oeis4.)