A031674 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 86.

1850, 16909, 46681, 91253, 151402, 224797, 226697, 313769, 316013, 417541, 425329, 537578, 540514, 676045, 682637, 984593, 990554, 994538, 1158401, 1162709, 1171349, 1180021, 1182194, 1364953, 1374313, 1563341, 1568345, 1573357, 1780517, 1783186, 1785857

Offset

1,1

Links

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

Mathematica

cfo86Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {0, 0}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[(len+1)/2]] == 86]; Select[Range[1800000], cfo86Q] (* Harvey P. Dale, Jul 31 2013 *)

Crossrefs

Sequence in context: A062670 A206468 A031764 * A031541 A031721 A224567

Adjacent sequences: A031671 A031672 A031673 * A031675 A031676 A031677

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected and extended by Harvey P. Dale, Jul 31 2013

Status

approved