G.f. A(x) satisfies A(x) = Product_{n>=1} (1 + x^n*A(x)^n).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =19a(5) =64a(6) =227a(7) =832a(8) =3125a(9) =11970a(10) =46579a(11) =183614a(12) =731688a(13) =2942673a(14) =11928707a(15) =48688888a(16) =199932987a(17) =825379993a(18) =3423614756a(19) =14261439594a(20) =59635806865a(21) =250241613688