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A041155
Denominators of continued fraction convergents to sqrt(87).
2
1, 3, 55, 168, 3079, 9405, 172369, 526512, 9649585, 29475267, 540204391, 1650088440, 30241796311, 92375477373, 1693000389025, 5171376644448, 94777779989089, 289504716611715, 5305862678999959, 16207092753611592, 297033532244008615, 907307689485637437
OFFSET
0,2
FORMULA
G.f.: (1 +3*x -x^2)/(x^4 -56*x^2 +1), - Vincenzo Librandi, Dec 12 2013
a(n) = 56*a(n-2) - a(n-4). - Vincenzo Librandi, Dec 12 2013
MATHEMATICA
Denominator/@Convergents[Sqrt[87], 50] (* Vladimir Joseph Stephan Orlovsky, Jul 05 2011 *)
CoefficientList[Series[(1 + 3 x - x^2)/(x^4 - 56 x^2 + 1), {x, 0, 30}], x] (* Vincenzo Librandi, Dec 12 2013 *)
PROG
(Magma) I:=[1, 3, 55, 168]; [n le 4 select I[n] else 56*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 12 2013
CROSSREFS
Cf. A041154.
Sequence in context: A088278 A242199 A268661 * A111483 A119152 A119061
KEYWORD
nonn,frac,easy
AUTHOR
STATUS
approved