a(n)= +a(n-3) +2*a(n-6) +a(n-9).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =1a(6) =3a(7) =6a(8) =3a(9) =6a(10) =13a(11) =6a(12) =13a(13) =28a(14) =13a(15) =28a(16) =60a(17) =28a(18) =60a(19) =129a(20) =60a(21) =129a(22) =277a(23) =129a(24) =277a(25) =595a(26) =277a(27) =595a(28) =1278a(29) =595