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

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =3a(5) =-15a(6) =-118a(7) =-336a(8) =-595a(9) =1467a(10) =20391a(11) =96205a(12) =353686a(13) =574786a(14) =-2717256a(15) =-30598208a(16) =-197828371a(17) =-841728699a(18) =-2599029153a(19) =-1309899955a(20) =56975269295a(21) =522707807733