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

Terms

a(0) =3a(1) =2a(2) =2a(3) =5a(4) =10a(5) =17a(6) =29a(7) =51a(8) =90a(9) =158a(10) =277a(11) =486a(12) =853a(13) =1497a(14) =2627a(15) =4610a(16) =8090a(17) =14197a(18) =24914a(19) =43721a(20) =76725a(21) =134643a(22) =236282a(23) =414646a(24) =727653a(25) =1276942a(26) =2240877a(27) =3932465a(28) =6900995a(29) =12110402