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A031573
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Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 75.
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0
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5627, 5639, 5643, 5647, 5651, 5659, 5667, 5683, 5711, 5723, 5731, 5739, 5743, 5763, 5767, 5779, 5783, 5787, 5791, 5807, 5827, 5831, 5839, 5843, 5851, 5867, 5879, 5891, 5899, 5903, 5923, 5927, 22504, 22528, 22624, 22656, 22688, 22696, 22720, 22784
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OFFSET
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1,1
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COMMENTS
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The "central term" is at period/2, not at period/2 + 1. - Harvey P. Dale, Feb 20 2013
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LINKS
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MATHEMATICA
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epQ[n_]:=Module[{srt=Sqrt[n], cf, len}, cf=If[IntegerQ[srt], {1}, ContinuedFraction[ srt] [[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]]==75]; Select[Range[ 23000], epQ] (* Harvey P. Dale, Feb 20 2013 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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