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 A031631 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 43. 0
 11689, 23458, 37717, 38890, 56765, 78569, 79693, 106501, 138673, 139418, 171757, 204745, 210205, 212041, 248533, 252533, 255554, 290069, 291146, 293306, 294389, 295474, 296561, 298741, 299834, 300929, 302026, 395225, 402797, 405337 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..30. MATHEMATICA cf43Q[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]] == 43]; Select[Range[406000], cf43Q] (* Harvey P. Dale, Aug 25 2019 *) CROSSREFS Sequence in context: A254777 A254723 A354212 * A250923 A015630 A237933 Adjacent sequences: A031628 A031629 A031630 * A031632 A031633 A031634 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS First term 1850 removed by Georg Fischer, Jun 16 2019 STATUS approved

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Last modified December 3 05:03 EST 2023. Contains 367531 sequences. (Running on oeis4.)