a(n) = (8^n+16*(-9)^n)/17.

Terms

a(0) =1a(1) =-8a(2) =80a(3) =-656a(4) =6416a(5) =-53648a(6) =515600a(7) =-4378256a(8) =41501456a(9) =-356735888a(10) =3344840720a(11) =-29029824656a(12) =269858356496