G.f. A(x) satisfies A( x*A(x) - A(x)^2 ) + A(x)^3 = 0.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =49a(6) =168a(7) =594a(8) =2150a(9) =7931a(10) =29718a(11) =112814a(12) =432957a(13) =1677049a(14) =6547840a(15) =25742301a(16) =101817960a(17) =404878296a(18) =1617682086a(19) =6491059057a(20) =26146200245a(21) =105685403259a(22) =428547336180