A031638 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 50.

626, 15901, 31378, 51157, 52522, 77405, 107753, 109069, 141601, 142354, 143866, 146149, 182618, 183473, 185189, 226937, 230761, 336929, 340418, 392501, 393754, 396266, 398786, 400049, 402581, 406394, 465853, 474073, 536665, 542537, 545485

Offset

1,1

Links

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

Mathematica

cf50Q[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]] == 50]; Select[Range[550000], cf50Q] (* Harvey P. Dale, May 13 2019 *)

Crossrefs

Sequence in context: A345766 A158383 A031728 * A098262 A031523 A345523

Adjacent sequences: A031635 A031636 A031637 * A031639 A031640 A031641

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected by Harvey P. Dale, May 13 2019

Status

approved