a(n) = (8*10^n - 17)/9 for n > 0.

Terms

a(0) =7a(1) =87a(2) =887a(3) =8887a(4) =88887a(5) =888887a(6) =8888887a(7) =88888887a(8) =888888887a(9) =8888888887a(10) =88888888887a(11) =888888888887