G.f. A(x) satisfies A(x) = 1 + x/A(x)^3 * (1 - A(x) + A(x)^4).

Terms

a(0) =1a(1) =1a(2) =0a(3) =3a(4) =-6a(5) =28a(6) =-105a(7) =444a(8) =-1897a(9) =8338a(10) =-37305a(11) =169471a(12) =-779537a(13) =3623500a(14) =-16993990a(15) =80316081a(16) =-382136133a(17) =1828896726a(18) =-8798796709a(19) =42528048930a(20) =-206413678447