a(n) = 7*10^n - 9.

Terms

a(0) =61a(1) =691a(2) =6991a(3) =69991a(4) =699991a(5) =6999991a(6) =69999991a(7) =699999991a(8) =6999999991a(9) =69999999991a(10) =699999999991