E.g.f. satisfies A(x) = exp(x*A(x^3/3!)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =21a(6) =61a(7) =211a(8) =1401a(9) =8065a(10) =37241a(11) =240021a(12) =1997821a(13) =14657501a(14) =105629525a(15) =958412911a(16) =9201199281a(17) =86311594881a(18) =871038486001