G.f. satisfies A(x) = 1 + x/(1 - x^3)^2 * A(x/(1 - x^3)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =6a(6) =10a(7) =18a(8) =42a(9) =94a(10) =193a(11) =428a(12) =1036a(13) =2470a(14) =5779a(15) =14192a(16) =36176a(17) =91649a(18) =233617a(19) =613978a(20) =1641492a(21) =4396393a(22) =11922501a(23) =32969768a(24) =92080274a(25) =258774392a(26) =736441673a(27) =2123145058a(28) =6168831095a(29) =18067587851