a(n) = 3^(n-1)*Fibonacci(n).

Terms

a(0) =0a(1) =1a(2) =3a(3) =18a(4) =81a(5) =405a(6) =1944a(7) =9477a(8) =45927a(9) =223074a(10) =1082565a(11) =5255361a(12) =25509168a(13) =123825753a(14) =601059771a(15) =2917611090a(16) =14162371209a(17) =68745613437a(18) =333698181192