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

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =11a(5) =42a(6) =167a(7) =685a(8) =2879a(9) =12338a(10) =53718a(11) =236961a(12) =1056825a(13) =4757575a(14) =21590295a(15) =98665559a(16) =453663399a(17) =2097270984a(18) =9742489832a(19) =45452945649a(20) =212884993100