G.f. A(x) satisfies A(x) = 1 + x/A(-x*A(x)^2)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =3a(4) =-8a(5) =-81a(6) =-462a(7) =-1140a(8) =1662a(9) =42210a(10) =341922a(11) =1588428a(12) =3968106a(13) =-17035461a(14) =-330216303a(15) =-2645037192a(16) =-15366663001a(17) =-56099904270a(18) =42126523152