a(n) = 10^n - n^6.

Terms

a(0) =1a(1) =9a(2) =36a(3) =271a(4) =5904a(5) =84375a(6) =953344a(7) =9882351a(8) =99737856a(9) =999468559a(10) =9999000000a(11) =99998228439a(12) =999997014016