A031546 Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 48.

2306, 2322, 2326, 2338, 2342, 2354, 2358, 2374, 2386, 2406, 2414, 2434, 2446, 2462, 2498, 5187, 5223, 5241, 5262, 5268, 5277, 5349, 5361, 5367, 5403, 5433, 5469, 5493, 5529, 5541, 5556, 5577, 5583, 5601, 5613, 5622, 9220, 9236, 9244, 9260, 9276, 9332

Offset

1,1

Links

Table of n, a(n) for n=1..42.

Mathematica

cf48Q[n_]:=Module[{c=Sqrt[n], cf, len}, cf=If[IntegerQ[c], 1, ContinuedFraction[ c][[2]]]; len=Length[cf]; EvenQ[ len]&&cf[[len/2]] == 48]; Select[ Range[ 10000], cf48Q] (* Harvey P. Dale, Jan 14 2013 *)

Crossrefs

Sequence in context: A338617 A274578 A031774 * A250874 A247698 A247839

Adjacent sequences: A031543 A031544 A031545 * A031547 A031548 A031549

Keyword

nonn

Author

David W. Wilson

Status

approved