a(n) = 7*6^n+1.

Terms

a(0) =8a(1) =43a(2) =253a(3) =1513a(4) =9073a(5) =54433a(6) =326593a(7) =1959553a(8) =11757313a(9) =70543873a(10) =423263233a(11) =2539579393a(12) =15237476353a(13) =91424858113a(14) =548549148673