a(2n+1) = 3^n, a(2n) = 4*3^(n-1) except for a(0) = 1.

Terms

a(0) =1a(1) =1a(2) =4a(3) =3a(4) =12a(5) =9a(6) =36a(7) =27a(8) =108a(9) =81a(10) =324a(11) =243a(12) =972a(13) =729a(14) =2916a(15) =2187a(16) =8748a(17) =6561a(18) =26244a(19) =19683a(20) =78732a(21) =59049a(22) =236196a(23) =177147a(24) =708588a(25) =531441a(26) =2125764a(27) =1594323a(28) =6377292a(29) =4782969