a(n) = 6*(10^n - 1).

Terms

a(0) =0a(1) =54a(2) =594a(3) =5994a(4) =59994a(5) =599994a(6) =5999994a(7) =59999994a(8) =599999994a(9) =5999999994a(10) =59999999994a(11) =599999999994