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 A031628 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 40. 0
 401, 10429, 20498, 32842, 33937, 68813, 90826, 92641, 94474, 178525, 180217, 213973, 214898, 216754, 251626, 252629, 253634, 254641, 256661, 257674, 259706, 262769, 344237, 346585, 348941, 353677, 386602, 392837, 396602, 400385, 439333, 443314, 449989 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..33. MATHEMATICA op40Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {0, 0}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[(len+1)/2]] ==40]; Select[Range[500000], op40Q] (* Harvey P. Dale, Dec 06 2015 *) CROSSREFS Subsequence of A003814. Sequence in context: A031718 A102324 A156785 * A179293 A097742 A115244 Adjacent sequences: A031625 A031626 A031627 * A031629 A031630 A031631 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS Corrected and extended by Harvey P. Dale, Dec 06 2015 STATUS approved

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Last modified May 28 19:55 EDT 2024. Contains 372919 sequences. (Running on oeis4.)