a(n) = 2^n - n^12.

Terms

a(0) =1a(1) =1a(2) =-4092a(3) =-531433a(4) =-16777200a(5) =-244140593a(6) =-2176782272a(7) =-13841287073a(8) =-68719476480a(9) =-282429535969a(10) =-999999998976