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A031584 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..40.

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: A347164 A206202 A034279 * A237311 A023940 A116195

Adjacent sequences:  A031581 A031582 A031583 * A031585 A031586 A031587

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified October 19 09:58 EDT 2021. Contains 348074 sequences. (Running on oeis4.)