OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (0,402,0,-1).
FORMULA
G.f.: -(x^2-10*x-1) / ((x^2-20*x-1)*(x^2+20*x-1)). - Colin Barker, Nov 24 2013
a(n) = 402*a(n-2) - a(n-4) for n>3. - Vincenzo Librandi, Dec 24 2013
MATHEMATICA
Denominator[Convergents[Sqrt[404], 30]] (* Vincenzo Librandi, Dec 24 2013 *)
PROG
(Magma) I:=[1, 10, 401, 4020]; [n le 4 select I[n] else 402*Self(n-2)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Dec 24 2013
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Nov 24 2013
STATUS
approved