a(n) = 8^n-7^n-6^n-5^n-4^n-3^n-2^n-1.

Terms

a(0) =-6a(1) =-20a(2) =-76a(3) =-272a(4) =-580a(5) =3760a(6) =77324a(7) =896848a(8) =8869820a(9) =81550960a(10) =719926124a(11) =6196609168a(12) =52439953820a(13) =438516694960