a(n) = 6^n - n^9.

Terms

a(0) =1a(1) =5a(2) =-476a(3) =-19467a(4) =-260848a(5) =-1945349a(6) =-10031040a(7) =-40073671a(8) =-132538112a(9) =-377342793a(10) =-939533824a(11) =-1995150635a(12) =-2982998016a(13) =2456194643a(14) =57703117312a(15) =431741625201