a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 2, a(1) = 0, a(2) = 2, a(3) = 1.

Terms

a(0) =2a(1) =0a(2) =2a(3) =1a(4) =3a(5) =5a(6) =8a(7) =12a(8) =20a(9) =33a(10) =53a(11) =85a(12) =138a(13) =224a(14) =362a(15) =585a(16) =947a(17) =1533a(18) =2480a(19) =4012a(20) =6492a(21) =10505a(22) =16997a(23) =27501a(24) =44498a(25) =72000a(26) =116498a(27) =188497a(28) =304995a(29) =493493