a(n) = 4^n*Lucas(n), where Lucas = A000032.

Terms

a(0) =2a(1) =4a(2) =48a(3) =256a(4) =1792a(5) =11264a(6) =73728a(7) =475136a(8) =3080192a(9) =19922944a(10) =128974848a(11) =834666496a(12) =5402263552a(13) =34963718144a(14) =226291089408