G.f. A(x) satisfies: A(x) = Product_{k>=1} 1/(1 - k*x^k*A(x)).

Terms

a(0) =1a(1) =1a(2) =4a(3) =14a(4) =55a(5) =217a(6) =908a(7) =3864a(8) =16894a(9) =75078a(10) =338862a(11) =1548055a(12) =7147427a(13) =33294790a(14) =156305144a(15) =738753341a(16) =3512431392a(17) =16788169689a(18) =80619590577a(19) =388785776751