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 A031675 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. 0
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..27. MATHEMATICA 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 *) CROSSREFS Sequence in context: A029754 A258892 A204473 * A254977 A238143 A110845 Adjacent sequences: A031672 A031673 A031674 * A031676 A031677 A031678 KEYWORD nonn AUTHOR David W. Wilson EXTENSIONS Definition clarified and terms corrected by Harvey P. Dale, Mar 25 2016 STATUS approved

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Last modified May 26 13:41 EDT 2024. Contains 372826 sequences. (Running on oeis4.)