OFFSET
0,2
COMMENTS
a(0)=1, a(2n-1)=k^(2n-1), a(2n)=(2-k)k^(2n-1), k=6, G.f.: (1+kx+(2-2k)kx^2)/((1-kx)(1+kx)), k=6.
LINKS
FORMULA
a(n)=6^n/6+(-5)(-6)^n/6+10*0^n/6
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Dec 19 2003
STATUS
approved