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

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =7a(5) =12a(6) =19a(7) =30a(8) =49a(9) =80a(10) =129a(11) =208a(12) =337a(13) =546a(14) =883a(15) =1428a(16) =2311a(17) =3740a(18) =6051a(19) =9790a(20) =15841a(21) =25632a(22) =41473a(23) =67104a(24) =108577a(25) =175682a(26) =284259a(27) =459940a(28) =744199a(29) =1204140