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

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =11a(5) =30a(6) =87a(7) =267a(8) =842a(9) =2711a(10) =8869a(11) =29394a(12) =98485a(13) =333038a(14) =1135194a(15) =3896244a(16) =13454040a(17) =46707272a(18) =162924504a(19) =570746300a(20) =2007110128a(21) =7082934600a(22) =25074540508a(23) =89024971896a(24) =316917263448