OFFSET
0,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (0,802,0,-1).
FORMULA
G.f.: -(x^3-20*x^2-401*x-20) / (x^4-802*x^2+1). - Vincenzo Librandi, Nov 08 2013, simplified by Colin Barker, Dec 28 2013
a(n) = 802*a(n-2)-a(n-4). - Vincenzo Librandi, Nov 08 2013, simplified by Colin Barker, Dec 28 2013
MATHEMATICA
Numerator[Convergents[Sqrt[402], 30]] (* Harvey P. Dale, Apr 29 2013 *)
CoefficientList[Series[(20 + 401 x + 16060 x^2 + 321601 x^3 + 16060 x^4 - 401 x^5 + 20 x^6 - x^7)/(1 - 643202 x^4 + x^8), {x, 0, 30}], x] (* Vincenzo Librandi, Nov 08 2013 *)
PROG
(Magma) I:=[20, 401, 16060, 321601, 12880100, 257923601, 10329824140, 206854406401]; [n le 8 select I[n] else 643202*Self(n-4)-Self(n-8): n in [1..30]]; // Vincenzo Librandi, Nov 08 2013
CROSSREFS
KEYWORD
nonn,frac,easy,less
AUTHOR
EXTENSIONS
Additional term from Colin Barker, Dec 28 2013
STATUS
approved