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A031662
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 74.
0
1370, 12553, 34621, 111637, 166585, 169865, 312706, 400978, 403514, 501625, 504461, 611965, 728138, 731554, 743573, 858101, 859954, 861809, 867386, 869249, 872981, 876721, 1158617, 1162925, 1167241, 1171565, 1180237, 1323461, 1328065, 1332677, 1339610
OFFSET
1,1
MATHEMATICA
cf74Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {2, 2}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len] && cf[[(len+1)/2]]==74]; Select[Range[1400000], cf74Q] (* Harvey P. Dale, Mar 15 2015 *)
CROSSREFS
Sequence in context: A145697 A045107 A031752 * A251567 A251562 A059082
KEYWORD
nonn
EXTENSIONS
Definition clarified and terms corrected and extended by Harvey P. Dale, Mar 15 2015
STATUS
approved