a(n) = a(n-1) + a(n-4); first four terms are 0,1,2,3.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =3a(5) =4a(6) =6a(7) =9a(8) =12a(9) =16a(10) =22a(11) =31a(12) =43a(13) =59a(14) =81a(15) =112a(16) =155a(17) =214a(18) =295a(19) =407a(20) =562a(21) =776a(22) =1071a(23) =1478a(24) =2040a(25) =2816a(26) =3887a(27) =5365a(28) =7405a(29) =10221