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

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =19a(5) =67a(6) =244a(7) =928a(8) =3608a(9) =14348a(10) =57936a(11) =237228a(12) =982006a(13) =4104266a(14) =17292220a(15) =73373704a(16) =313255939a(17) =1344703363a(18) =5800347378a(19) =25128400374a(20) =109287352255a(21) =476990070863