a(n) = 6*(10^n-5).

Terms

a(0) =30a(1) =570a(2) =5970a(3) =59970a(4) =599970a(5) =5999970a(6) =59999970a(7) =599999970a(8) =5999999970a(9) =59999999970a(10) =599999999970