a(n) = 3*a(n-1) - 2*a(n-2) - a(n-3) + a(n-4), where a(1) = 1, a(2) = 3, a(3) = 5, a(4) = 8.

Terms

a(0) =1a(1) =3a(2) =5a(3) =8a(4) =12a(5) =18a(6) =27a(7) =41a(8) =63a(9) =98a(10) =154a(11) =244a(12) =389a(13) =623a(14) =1001a(15) =1612a(16) =2600a(17) =4198a(18) =6783a(19) =10965a(20) =17731a(21) =28678a(22) =46390a(23) =75048a(24) =121417a(25) =196443a(26) =317837a(27) =514256a(28) =832068a(29) =1346298