G.f.: Sum_{n>=1} G_n(x)^n where G_n(x) = x + x*G_n(x)^n.

Terms

a(0) =1a(1) =2a(2) =2a(3) =4a(4) =2a(5) =10a(6) =2a(7) =20a(8) =14a(9) =49a(10) =2a(11) =217a(12) =2a(13) =438a(14) =310a(15) =1580a(16) =2a(17) =6352a(18) =2a(19) =18062a(20) =7824a(21) =58799a(22) =2a(23) =258971a(24) =2532a(25) =742915a(26) =246794a(27) =2729095a(28) =2a(29) =11154954