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 A031679 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 91. 0
 52009, 169825, 170650, 252125, 350633, 466714, 474946, 600914, 604018, 605573, 757261, 760745, 914377, 925885, 929737, 1098833, 1103029, 1109338, 1113554, 1117778, 1297946, 1302506, 1304789, 1313941, 1316234, 1318529, 1320826 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..27. MATHEMATICA cf91Q[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]] == 91]; Select[Range[14*10^5], cf91Q] (* Harvey P. Dale, Sep 23 2018 *) CROSSREFS Sequence in context: A253996 A258906 A234181 * A234679 A191303 A291869 Adjacent sequences: A031676 A031677 A031678 * A031680 A031681 A031682 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS Corrected by Harvey P. Dale, Sep 23 2018 STATUS approved

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Last modified December 2 13:03 EST 2023. Contains 367517 sequences. (Running on oeis4.)