OFFSET
0,2
FORMULA
a(n)=(3^n - 1)*(3^n + 1)/2^(4 - Mod[n, 2]).
a(n)=82*a(n-2)-81*a(n-4). G.f.: (1+5x+9x^2)/((1-x)(1-9x)(1+x)(1+9x)). [From R. J. Mathar, Dec 04 2008]
MATHEMATICA
Clear[a, n];
a[n_] :=(3^n - 1)*(3^n + 1)/2^(4 - Mod[n, 2]);
Table[a[n], {n, 0, 30}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Roger L. Bagula, Dec 02 2008
STATUS
approved