OFFSET
0,3
LINKS
FORMULA
G.f.: (1 - 2*x) / (1 - x - 6*x^2).
a(n) = a(n-1) + 6*a(n-2) for n>1, a(0)=1, a(1)=-1.
a(n) = sum_{k=0..n} A108561(n,k)*2^k.
From Bruno Berselli, Nov 18 2013: (Start)
a(n) = (3^n + 4*(-2)^n)/5.
a(n+1) + a(n) = 4*A015441(n).
a(n+1) - a(n) = -2*(-1)^n*A165405(n).
Sum(a(i), i=0..n) = A091001(n+1). (End)
MATHEMATICA
Table[(3^n + 4 (-2)^n)/5, {n, 0, 30}] (* Bruno Berselli, Nov 18 2013 *)
CoefficientList[Series[(1-2x)/((1+2x)(1-3x)), {x, 0, 40}], x] (* or *) LinearRecurrence[ {1, 6}, {1, -1}, 30] (* Harvey P. Dale, Apr 20 2017 *)
PROG
(PARI) Vec((1-2*x)/((1+2*x)*(1-3*x))+O(x^20)) \\ Edward Jiang, Sep 06 2014
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Philippe Deléham, Nov 17 2013
STATUS
approved