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

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =10a(5) =19a(6) =36a(7) =69a(8) =134a(9) =258a(10) =497a(11) =958a(12) =1847a(13) =3560a(14) =6862a(15) =13227a(16) =25496a(17) =49145a(18) =94730a(19) =182598a(20) =351969a(21) =678442a(22) =1307739a(23) =2520748a(24) =4858898a(25) =9365827a(26) =18053212a(27) =34798685a(28) =67076622a(29) =129294346