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

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =-3a(5) =-50a(6) =-244a(7) =-714a(8) =-530a(9) =8522a(10) =63548a(11) =259473a(12) =535647a(13) =-1321437a(14) =-19094684a(15) =-103022071a(16) =-322370363a(17) =-142186810a(18) =5537336460a(19) =41081448638a(20) =170484444654a(21) =332739198585