G.f. satisfies: A(x) = exp( Sum_{n>=1} (A(x) - (-1)^n)^n * x^n/n ).

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =42a(5) =158a(6) =618a(7) =2498a(8) =10360a(9) =43832a(10) =188420a(11) =820608a(12) =3613212a(13) =16057640a(14) =71933768a(15) =324482500a(16) =1472604586a(17) =6719100254a(18) =30804229858a(19) =141829955338a(20) =655541387406