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

Terms

a(0) =2a(1) =1a(2) =1a(3) =1a(4) =4a(5) =6a(6) =8a(7) =13a(8) =23a(9) =37a(10) =58a(11) =94a(12) =154a(13) =249a(14) =401a(15) =649a(16) =1052a(17) =1702a(18) =2752a(19) =4453a(20) =7207a(21) =11661a(22) =18866a(23) =30526a(24) =49394a(25) =79921a(26) =129313a(27) =209233a(28) =338548a(29) =547782