a(n) = a(n-1) + a(n-3) + a(n-4), where a(0) = 1, a(1) = 2, a(2) = 5, a(3) = 7.

Terms

a(0) =1a(1) =2a(2) =5a(3) =7a(4) =10a(5) =17a(6) =29a(7) =46a(8) =73a(9) =119a(10) =194a(11) =313a(12) =505a(13) =818a(14) =1325a(15) =2143a(16) =3466a(17) =5609a(18) =9077a(19) =14686a(20) =23761a(21) =38447a(22) =62210a(23) =100657a(24) =162865a(25) =263522a(26) =426389a(27) =689911a(28) =1116298a(29) =1806209