a(n) = 4*a(n-2) - 2*a(n-4).

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =4a(5) =10a(6) =14a(7) =34a(8) =48a(9) =116a(10) =164a(11) =396a(12) =560a(13) =1352a(14) =1912a(15) =4616a(16) =6528a(17) =15760a(18) =22288a(19) =53808a(20) =76096a(21) =183712a(22) =259808a(23) =627232a(24) =887040a(25) =2141504a(26) =3028544a(27) =7311552a(28) =10340096a(29) =24963200