a(n) = 4*a(n-1) + 4*a(n-2), a(0)=1, a(1)=2.

Terms

a(0) =1a(1) =2a(2) =12a(3) =56a(4) =272a(5) =1312a(6) =6336a(7) =30592a(8) =147712a(9) =713216a(10) =3443712a(11) =16627712a(12) =80285696a(13) =387653632a(14) =1871757312a(15) =9037643776a(16) =43637604352a(17) =210700992512