G.f. = b(2)*b(4)*b(6)/(x^8+x^6-x^5-x^3-x+1), where b(k) = (1-x^k)/(1-x).

Terms

a(0) =1a(1) =4a(2) =9a(3) =17a(4) =29a(5) =47a(6) =74a(7) =113a(8) =170a(9) =253a(10) =375a(11) =555a(12) =818a(13) =1203a(14) =1767a(15) =2594a(16) =3807a(17) =5584a(18) =8188a(19) =12004a(20) =17597a(21) =25795a(22) =37809a(23) =55416a(24) =81220a(25) =119038a(26) =174464a(27) =255694a(28) =374742a(29) =549215