G.f. = b(2)*b(4)*b(6)/(x^8+x^7-x^3-x^2-x+1), where b(k) = (1-x^k)/(1-x).

Terms

a(0) =1a(1) =4a(2) =10a(3) =22a(4) =44a(5) =84a(6) =157a(7) =289a(8) =528a(9) =961a(10) =1746a(11) =3169a(12) =5748a(13) =10422a(14) =18893a(15) =34246a(16) =62072a(17) =112504a(18) =203907a(19) =369566a(20) =669807a(21) =1213965a(22) =2200199a(23) =3987653a(24) =7227241a(25) =13098682a(26) =23740103a(27) =43026653a(28) =77981666a(29) =141334258