a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 1, a(1) = 2, a(2) = 4, a(3) = 8.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =11a(5) =17a(6) =29a(7) =48a(8) =76a(9) =122a(10) =199a(11) =323a(12) =521a(13) =842a(14) =1364a(15) =2208a(16) =3571a(17) =5777a(18) =9349a(19) =15128a(20) =24476a(21) =39602a(22) =64079a(23) =103683a(24) =167761a(25) =271442a(26) =439204a(27) =710648a(28) =1149851a(29) =1860497