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

Terms

a(0) =1a(1) =4a(2) =10a(3) =21a(4) =40a(5) =74a(6) =135a(7) =244a(8) =438a(9) =782a(10) =1394a(11) =2484a(12) =4425a(13) =7880a(14) =14028a(15) =24969a(16) =44442a(17) =79102a(18) =140792a(19) =250588a(20) =446002a(21) =793801a(22) =1412820a(23) =2514562a(24) =4475459a(25) =7965488a(26) =14177086a(27) =25232574a(28) =44909290a(29) =79930188