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, 0, 0, 880, 0, 0, 0, -1).
FORMULA
G.f.: (20 +21*x +419*x^2 +440*x^3 +419*x^4 -21*x^5 +20*x^6 -x^7)/(1 -880*x^4 +x^8). - Vincenzo Librandi, Nov 10 2013
a(n) = 880*a(n-4)-a(n-8). - Vincenzo Librandi, Nov 10 2013
MATHEMATICA
Numerator[Convergents[Sqrt[439], 30]] (* or *) CoefficientList[Series[(20 + 21 x + 419 x^2 + 440 x^3 + 419 x^4 - 21 x^5 + 20 x^6 - x^7)/(1 - 880 x^4 + x^8), {x, 0, 25}], x] (* Vincenzo Librandi, Nov 10 2013 *)
LinearRecurrence[{0, 0, 0, 880, 0, 0, 0, -1}, {20, 21, 419, 440, 18019, 18459, 368740, 387199}, 20] (* Harvey P. Dale, Aug 29 2020 *)
PROG
(Magma) I:=[20, 21, 419, 440, 18019, 18459, 368740, 387199]; [n le 8 select I[n] else 880*Self(n-4)-Self(n-8): n in [1..25]]; // Vincenzo Librandi, Nov 10 2013
CROSSREFS
KEYWORD
nonn,cofr,frac,easy,less
AUTHOR
STATUS
approved