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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =17a(5) =51a(6) =163a(7) =533a(8) =1779a(9) =6055a(10) =20908a(11) =73052a(12) =257863a(13) =918139a(14) =3293538a(15) =11891778a(16) =43183835a(17) =157616827a(18) =577902846a(19) =2127539802a(20) =7861397403a(21) =29145629141a(22) =108385383175a(23) =404184619545