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A031668 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 80. 0
40829, 132577, 195485, 197257, 362629, 365041, 466778, 473633, 584057, 587117, 590185, 850613, 852458, 1002626, 1006634, 1014674, 1016689, 1018706, 1024769, 1184473, 1188829, 1351085, 1360397, 1365065, 1374425, 1541042, 1548497 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
cf80Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {0, 0}, ContinuedFraction[s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[Floor[len/2]]]==cf[[Ceiling[len/2]]]==80]; Select[Range[155*10^4], cf80Q] (* Harvey P. Dale, Jul 24 2022 *)
CROSSREFS
Subsequence of A003814.
Sequence in context: A097238 A249879 A046180 * A164648 A232301 A212080
KEYWORD
nonn
AUTHOR
EXTENSIONS
First term 6401 removed by Georg Fischer, Jun 16 2019
STATUS
approved

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Last modified June 13 00:51 EDT 2024. Contains 373362 sequences. (Running on oeis4.)