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A031541
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 43.
0
1851, 1867, 1871, 1879, 1899, 1907, 1923, 1927, 1931, 1951, 1979, 1987, 1999, 2003, 2011, 2023, 7400, 7424, 7488, 7520, 7528, 7552, 7584, 7592, 7624, 7680, 7712, 7720, 7776, 7808, 7872, 7880, 7904, 7976, 8000, 8032, 8096, 16647, 16707, 16719, 16791
OFFSET
1,1
MATHEMATICA
cf43Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]] == 43]; Select[Range[17000], cf43Q] (* Harvey P. Dale, Jan 08 2019 *)
CROSSREFS
Sequence in context: A206468 A031764 A031674 * A031721 A224567 A303272
KEYWORD
nonn
EXTENSIONS
Definition corrected by Harvey P. Dale, Feb 24 2023
STATUS
approved