OFFSET
1,2
FORMULA
a(n)=6*a(n-1)-12*a(n-2)+10*a(n-3)-3*a(n-4)+2
a(n)=7*a(n-1)-18*a(n-2)+22*a(n-3)-13*a(n-4)+3*a(n-5)
a(n):= -1/6*n^3-n^2-7/3*n-9/4+9/4*3^n
G.f.: GF4(z;m=1) = z*(1+z)/((1-3*z)*(1-z)^4)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Johannes W. Meijer, Feb 20 2009
STATUS
approved