A031680 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 92.

2117, 53849, 104378, 105674, 172306, 173137, 258185, 360169, 477706, 481861, 771245, 778285, 937465, 1128373, 1327729, 1332341, 1336961, 1339274, 1341589, 1343906, 1563229, 1807177, 1817945, 2051585, 2057317, 2060186, 2063057, 2065930

Offset

1,1

Links

Table of n, a(n) for n=1..28.

Mathematica

opcf92Q[n_]:=Module[{sr=Sqrt[n], cf, len}, cf=ContinuedFraction[sr]; If[IntegerQ[sr], len=2, len=Length[cf[[2]]]]; OddQ[len]&&cf[[2]][[Ceiling[len/2]]]==92]; Select[Range[2100000], opcf92Q] (* Harvey P. Dale, Mar 29 2014 *)

Crossrefs

Sequence in context: A324170 A324324 A031770 * A031544 A205660 A205949

Adjacent sequences: A031677 A031678 A031679 * A031681 A031682 A031683

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected by and definition modified by Harvey P. Dale, Mar 29 2014

Status

approved