A031789 - OEIS

A031789

Period of continued fraction for sqrt(n) contains exactly 21 ones.

2575, 8383, 9919, 11659, 11771, 13375, 14999, 16891, 17875, 18067, 18232, 18415, 20087, 22355, 24568, 27083, 27783, 29727, 34867, 35875, 38056, 40067, 41987, 42319, 44063, 44455, 46343, 48168, 48216, 50856, 52219, 52507, 52871, 53387, 53447, 54487

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..36.

MATHEMATICA

cf21Q[n_]:=With[{s=Sqrt[n]}, If[IntegerQ[s], 1, Count[ContinuedFraction[s][[2]], 1]]==21]; Select[ Range[55000], cf21Q] (* Harvey P. Dale, May 19 2024 *)

CROSSREFS

Sequence in context: A156627 A175016 A260104 * A001294 A109026 A217183

Adjacent sequences: A031786 A031787 A031788 * A031790 A031791 A031792

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved