a(n) = a(n-2) + 2*a(n-3) for n >= 3, where a(0) = 2, a(2) = 4, a(3) = 5.

Terms

a(0) =2a(1) =4a(2) =5a(3) =8a(4) =13a(5) =18a(6) =29a(7) =44a(8) =65a(9) =102a(10) =153a(11) =232a(12) =357a(13) =538a(14) =821a(15) =1252a(16) =1897a(17) =2894a(18) =4401a(19) =6688a(20) =10189a(21) =15490a(22) =23565a(23) =35868a(24) =54545a(25) =82998a(26) =126281a(27) =192088a(28) =292277a(29) =444650