G.f. A(x) satisfies A(x/A(x)) = 1/(1-x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =118a(6) =674a(7) =4308a(8) =30062a(9) =225266a(10) =1791964a(11) =15009118a(12) =131566314a(13) =1201452248a(14) =11389283418a(15) =111761444078