OFFSET
0,2
COMMENTS
a(n+1) - 4a(n)= period 2: repeat -2, 3.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (4,1,-4)
FORMULA
a(n) = 4*a(n-1) + a(n-2) - 4*a(n-3).
G.f.: ( 1 - 2*x + 2*x^2 ) / ( (x-1)*(4*x-1)*(1+x) ). - R. J. Mathar, Nov 21 2011
MATHEMATICA
LinearRecurrence[{4, 1, -4}, {1, 2, 11}, 30] (* Harvey P. Dale, Sep 17 2013 *)
PROG
(Magma) [-1/6+(1/2)*(-1)^n+(2/3)*4^n: n in [0..25]]; // Vincenzo Librandi, Aug 09 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, May 26 2008
STATUS
approved