a(n) = 10^n - 3.

Terms

a(0) =7a(1) =97a(2) =997a(3) =9997a(4) =99997a(5) =999997a(6) =9999997a(7) =99999997a(8) =999999997a(9) =9999999997a(10) =99999999997a(11) =999999999997