G.f. satisfies A(x) = 1 + x*A(x)*f(x)^3, where f(x) = Sum_{k>=0} x^((4^k-1)/3).

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =26a(5) =69a(6) =184a(7) =488a(8) =1294a(9) =3436a(10) =9116a(11) =24190a(12) =64190a(13) =170334a(14) =451994a(15) =1199400a(16) =3182706a(17) =8445556a(18) =22410946a(19) =59469200a(20) =157806184a(21) =418751069a(22) =1111188772a(23) =2948626472a(24) =7824411358a(25) =20762688580a(26) =55095420880a(27) =146200015984