OFFSET
0,1
LINKS
Indranil Ghosh, Table of n, a(n) for n = 0..3314
Index entries for linear recurrences with constant coefficients, signature (2,1,-2).
FORMULA
G.f.: (4-4x-2x^2)/(1-2x-x^2+2x^3). a(n)=2^(n+1)+1+(-1)^n.
MATHEMATICA
CoefficientList[Series[(4 - 4x - 2x^2)/(1 - 2x - x^2 + 2x^3), {x, 0, 30}], x]
PROG
(PARI) a(n)=2<<n+1+(-1)^n \\ Charles R Greathouse IV, Aug 20 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mario Catalani (mario.catalani(AT)unito.it), Aug 31 2003
STATUS
approved