a(n) = 2*a(n-2) + 4*a(n-3), with initial terms 0, 3, 3.

Terms

a(0) =0a(1) =3a(2) =3a(3) =6a(4) =18a(5) =24a(6) =60a(7) =120a(8) =216a(9) =480a(10) =912a(11) =1824a(12) =3744a(13) =7296a(14) =14784a(15) =29568a(16) =58752a(17) =118272a(18) =235776a(19) =471552a(20) =944640a(21) =1886208a(22) =3775488a(23) =7550976a(24) =15095808a(25) =30203904a(26) =60395520a(27) =120791040a(28) =241606656a(29) =483164160