OFFSET
1,1
LINKS
FORMULA
O.g.f.: -x*(5-7*x+4*x^2)/((-1+x)^2*(-1+3*x)). - R. J. Mathar, Jan 07 2008
EXAMPLE
a(3) = 2*3^3 + 3^2 - 4 = 2*27 + 9 - 4.
MAPLE
MATHEMATICA
Table[2*3^n + 3^(n - 1) - (n + 1), {n, 1, 50}] (* Stefan Steinerberger, Sep 20 2007 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, Sep 19 2007
STATUS
approved