Largest prime <= 9^n.

Terms

a(0) =7a(1) =79a(2) =727a(3) =6553a(4) =59029a(5) =531383a(6) =4782961a(7) =43046623a(8) =387420479a(9) =3486784393a(10) =31381059607a(11) =282429536453