a(n) = n*8^n + 1.

Terms

a(0) =1a(1) =9a(2) =129a(3) =1537a(4) =16385a(5) =163841a(6) =1572865a(7) =14680065a(8) =134217729a(9) =1207959553a(10) =10737418241a(11) =94489280513a(12) =824633720833