A031629 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 41.

3853, 35050, 35425, 51197, 53021, 71993, 74153, 95089, 96946, 122789, 124193, 126314, 152461, 154025, 157177, 190537, 223313, 228058, 230929, 232853, 266881, 267914, 268949, 269986, 273109, 274154, 275201, 314329, 363245, 368077, 409282

Offset

1,1

Links

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

Mathematica

cf41Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[(len+1)/2]] == 41]; Select[Range[410000], cf41Q] (* Harvey P. Dale, Jun 21 2019 *)

Crossrefs

Sequence in context: A234918 A015069 A015070 * A220752 A257780 A068267

Adjacent sequences: A031626 A031627 A031628 * A031630 A031631 A031632

Keyword

nonn

Author

David W. Wilson

Extensions

First term 1682 removed by Georg Fischer, Jun 16 2019

Status

approved