a(n) = (4*2^n + (-8)^n)/5.

Terms

a(0) =1a(1) =0a(2) =16a(3) =-96a(4) =832a(5) =-6528a(6) =52480a(7) =-419328a(8) =3355648a(9) =-26843136a(10) =214749184a(11) =-1717985280a(12) =13743898624a(13) =-109951156224a(14) =879609315328