OFFSET
0,1
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.: (26 +105*x +26*x^2 -x^3)/(1 -210*x^2 +x^4). - Vincenzo Librandi Nov 21 2013
a(n) = 210*a(n-2) - a(n-4). - Vincenzo Librandi, Nov 21 2013
MATHEMATICA
Numerator[Convergents[Sqrt[689], 30]] (* or *) CoefficientList[Series[(26 + 105 x + 26 x^2 - x^3)/(1 -210 x^2 + x^4), {x, 0, 30}], x] (* Vincenzo Librandi, Nov 21 2013 *)
LinearRecurrence[{0, 210, 0, -1}, {26, 105, 5486, 22049}, 20] (* Harvey P. Dale, May 12 2017 *)
PROG
(Magma) I:=[26, 105, 5486, 22049]; [n le 4 select I[n] else 210*Self(n-2)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Nov 21 2013
CROSSREFS
KEYWORD
nonn,cofr,frac,easy
AUTHOR
STATUS
approved