a(n) = 10^n - n^2.

Terms

a(0) =1a(1) =9a(2) =96a(3) =991a(4) =9984a(5) =99975a(6) =999964a(7) =9999951a(8) =99999936a(9) =999999919a(10) =9999999900a(11) =99999999879a(12) =999999999856