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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =16a(6) =59a(7) =246a(8) =1131a(9) =5655a(10) =30428a(11) =174835a(12) =1066334a(13) =6870542a(14) =46581883a(15) =331237074a(16) =2463361903a(17) =19112314727a(18) =154364077009