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A042307
Denominators of continued fraction convergents to sqrt(680).
2
1, 13, 677, 8814, 459005, 5975879, 311204713, 4051637148, 210996336409, 2747004010465, 143055204880589, 1862464667458122, 96991217912702933, 1262748297532596251, 65759902689607707985, 856141483262432800056, 44585117032336113310897
OFFSET
0,2
FORMULA
G.f.: -(x^2-13*x-1) / ((x^2-26*x-1)*(x^2+26*x-1)). - Colin Barker, Dec 07 2013
a(n) = 678*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Jan 19 2014
MATHEMATICA
Denominator[Convergents[Sqrt[680], 30]] (* Vincenzo Librandi, Jan 19 2014 *)
PROG
(Magma) I:=[1, 13, 677, 8814]; [n le 4 select I[n] else 678*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jan 19 2014
CROSSREFS
Sequence in context: A092547 A298951 A157027 * A012746 A211094 A290166
KEYWORD
nonn,frac,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Dec 07 2013
STATUS
approved