a(n+2) = 4*a(n), with a(0)=1, a(1)=3.

Terms

a(0) =1a(1) =3a(2) =4a(3) =12a(4) =16a(5) =48a(6) =64a(7) =192a(8) =256a(9) =768a(10) =1024a(11) =3072a(12) =4096a(13) =12288a(14) =16384a(15) =49152a(16) =65536a(17) =196608a(18) =262144a(19) =786432a(20) =1048576a(21) =3145728a(22) =4194304a(23) =12582912a(24) =16777216a(25) =50331648a(26) =67108864a(27) =201326592a(28) =268435456a(29) =805306368