OFFSET
1,1
COMMENTS
This sequence is identical to the sequence of numbers of the form k = a^2 + b, where a and b are positive integers and b is a factor of 2a greater than 1, in which case the continued fraction expansion of sqrt(k) is [a; [2a/b, 2a]]. - David Terr, Jun 11 2004
REFERENCES
Kenneth H. Rosen, Elementary Number Theory and Its Applications, Addison-Wesley, 1984, page 426 (but beware of errors!)
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
MATHEMATICA
cf2Q[n_]:=Module[{s=Sqrt[n]}, If[IntegerQ[s], 1, Length[ ContinuedFraction[ s][[2]]]]==2]; Select[Range[300], cf2Q] (* Harvey P. Dale, Jun 21 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved