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.

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

Links

Table of n, a(n) for n=1..31.

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

Adjacent sequences: A031659 A031660 A031661 * A031663 A031664 A031665

Keyword

nonn

Author

David W. Wilson

Extensions

Definition clarified and terms corrected and extended by Harvey P. Dale, Mar 15 2015

Status

approved