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A031641 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 53. 0
17981, 35018, 35393, 57202, 58162, 58645, 85385, 161026, 163441, 209138, 210053, 254377, 258425, 260461, 262505, 372629, 376298, 384929, 441521, 444181, 446849, 448186, 450866, 454901, 516253, 522013, 530713, 596825, 603017, 606125, 609241 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

cf53Q[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]] == 53]; Select[Range[610000], cf53Q] (* Harvey P. Dale, Jul 14 2017 *)

CROSSREFS

Sequence in context: A345869 A345585 A345842 * A106769 A224571 A251832

Adjacent sequences:  A031638 A031639 A031640 * A031642 A031643 A031644

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected and extended by Harvey P. Dale, Jul 14 2017

STATUS

approved

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Last modified June 29 09:21 EDT 2022. Contains 354910 sequences. (Running on oeis4.)