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A031584
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 86.
0
7398, 7414, 7438, 7446, 7454, 7458, 7478, 7506, 7534, 7542, 7554, 7558, 7586, 7606, 7634, 7646, 7654, 7666, 7682, 7694, 7698, 7702, 7718, 7726, 7734, 7742, 16644, 16653, 16671, 16689, 16743, 16773, 16782, 16788, 16809, 16833, 16869, 16917, 16941, 16953
OFFSET
1,1
MATHEMATICA
cf86Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]] == 86]; Select[ Range[17000], cf86Q] (* Harvey P. Dale, Jan 15 2019 *)
CROSSREFS
Sequence in context: A206202 A364182 A034279 * A237311 A023940 A116195
KEYWORD
nonn
STATUS
approved