a(n) = 8^n-n^6.

Terms

a(0) =1a(1) =7a(2) =0a(3) =-217a(4) =0a(5) =17143a(6) =215488a(7) =1979503a(8) =16515072a(9) =133686287a(10) =1072741824a(11) =8588163031a(12) =68716490752a(13) =549750987079