A031574 - OEIS

A031574

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 76.

5778, 5794, 5806, 5822, 5826, 5854, 5862, 5874, 5878, 5926, 5938, 5942, 5958, 5998, 6018, 6022, 6038, 6046, 6062, 6082, 12999, 13017, 13044, 13071, 13089, 13143, 13173, 13182, 13188, 13251, 13254, 13269, 13287, 13323, 13326, 13341, 13353, 13377, 13389

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..39.

MATHEMATICA

cf76Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]]== 76]; Select[ Range[14000], cf76Q] (* Harvey P. Dale, Aug 27 2019 *)

CROSSREFS

Sequence in context: A094411 A212423 A004933 * A004953 A004973 A114361

Adjacent sequences: A031571 A031572 A031573 * A031575 A031576 A031577

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved