A031667 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 79.

39229, 128245, 191965, 268493, 355441, 357829, 451873, 458618, 565865, 568877, 571897, 689341, 832273, 843253, 976769, 984689, 986674, 988661, 992641, 994634, 996629, 998626, 1149913, 1327945, 1332557, 1504037, 1508945, 1513861, 1526186, 1531130, 1536082

Offset

1,1

Links

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

Mathematica

op79Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len] && cf[[Floor[ len/2]+1]] == 79]; Select[Range[1600000], op79Q] (* Harvey P. Dale, Aug 04 2013 *)

Crossrefs

Sequence in context: A224622 A233955 A250515 * A196200 A274128 A144306

Adjacent sequences: A031664 A031665 A031666 * A031668 A031669 A031670

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected and extended by Harvey P. Dale, Aug 04 2013

Status

approved