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

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =7a(5) =10a(6) =21a(7) =31a(8) =60a(9) =91a(10) =167a(11) =258a(12) =457a(13) =715a(14) =1236a(15) =1951a(16) =3315a(17) =5266a(18) =8837a(19) =14103a(20) =23452a(21) =37555a(22) =62031a(23) =99586a(24) =163665a(25) =263251a(26) =431012a(27) =694263a(28) =1133467a(29) =1827730