a(n) = 11^n + 8^n - 1.

Terms

a(0) =1a(1) =18a(2) =184a(3) =1842a(4) =18736a(5) =193818a(6) =2033704a(7) =21584322a(8) =231136096a(9) =2492165418a(10) =27011166424a(11) =293901605202