A031685 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 97.

59561, 191050, 193681, 530209, 537514, 680914, 685873, 692513, 857837, 865261, 1248218, 1250453, 1259413, 1471994, 1474421, 1479281, 1481714, 1484149, 1486586, 1491466, 1496354, 1498801, 1722073, 1737853, 1748413, 1988941, 1994585

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Mathematica

cfop97Q[n_]:=Module[{s=Sqrt[n], cf, len}, If[IntegerQ[s], cf={1, 1}, cf = ContinuedFraction[s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[ (len+1)/2]] ==97]; Select[Range[2*10^6], cfop97Q] (* Harvey P. Dale, Dec 16 2014 *)

Crossrefs

Sequence in context: A224972 A104919 A135325 * A238077 A344358 A344359

Adjacent sequences: A031682 A031683 A031684 * A031686 A031687 A031688

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected by Harvey P. Dale, Dec 16 2014

Status

approved