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A031568
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 70.
0
4902, 4918, 4934, 4942, 4946, 4962, 4978, 4994, 5006, 5026, 5058, 5062, 5074, 5078, 5086, 5094, 5102, 5126, 5142, 5154, 5158, 5182, 11028, 11037, 11073, 11091, 11121, 11127, 11157, 11163, 11166, 11172, 11181, 11199, 11217, 11301, 11337, 11343, 11361
OFFSET
1,1
MATHEMATICA
cf70Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; EvenQ[len]&&cf[[len/2]] == 70]; Select[Range[11400], cf70Q] (* Harvey P. Dale, May 31 2021 *)
CROSSREFS
Sequence in context: A374500 A107545 A256363 * A083607 A168028 A031834
KEYWORD
nonn
STATUS
approved