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

Terms

a(0) =1a(1) =1a(2) =5a(3) =20a(4) =104a(5) =546a(6) =3066a(7) =17655a(8) =104555a(9) =630773a(10) =3867617a(11) =24020932a(12) =150827740a(13) =955808680a(14) =6105327912a(15) =39268000188a(16) =254093573088