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A031658
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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 70.
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0
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1226, 61553, 99937, 100570, 101842, 150665, 209933, 276901, 356698, 360289, 362693, 363898, 443917, 446585, 449261, 454637, 651778, 659873, 661498, 664754, 768001, 769754, 771509, 773266, 778549, 780314, 782081, 1037165, 1041241, 1045325, 1049417
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..31.
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MATHEMATICA
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cf70Q[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]] == 70]; Select[Range[11 10^5], cf70Q] (* Harvey P. Dale, Jul 24 2017 *)
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CROSSREFS
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Sequence in context: A218273 A046177 A031748 * A031533 A031713 A259998
Adjacent sequences: A031655 A031656 A031657 * A031659 A031660 A031661
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson
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EXTENSIONS
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Corrected and extended and definition clarified by Harvey P. Dale, Jul 24 2017
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STATUS
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approved
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