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A031675
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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 87.
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0
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94298, 153745, 155317, 156106, 430561, 434506, 547889, 550853, 555314, 689261, 692585, 695917, 839497, 846841, 1010554, 1014578, 1184369, 1190906, 1193089, 1195274, 1201841, 1204034, 1206229, 1208426, 1388413, 1603597, 1608665
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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cf87Q[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]] == 87]; Select[Range[1610000], cf87Q] (* Harvey P. Dale, Mar 25 2016 *)
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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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Definition clarified and terms corrected by Harvey P. Dale, Mar 25 2016
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STATUS
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approved
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