OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (0, 210, 0, -1).
FORMULA
G.f.: -(x^2-4*x-1) / (x^4-210*x^2+1). - Colin Barker, Dec 07 2013
a(n) = 210*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Jan 20 2014
MATHEMATICA
Denominator[Convergents[Sqrt[689], 30]] (* Vincenzo Librandi, Jan 20 2014 *)
LinearRecurrence[{0, 210, 0, -1}, {1, 4, 209, 840}, 20] (* Harvey P. Dale, Sep 26 2023 *)
PROG
(Magma) I:=[1, 4, 209, 840]; [n le 4 select I[n] else 210*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jan 20 2014
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Dec 07 2013
STATUS
approved