G.f. satisfies A(x) = 1 + x*A(x)^2 / (1 + x*A(x)^4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =-2a(4) =-14a(5) =-27a(6) =70a(7) =625a(8) =1457a(9) =-3541a(10) =-37403a(11) =-98547a(12) =207098a(13) =2564079a(14) =7448923a(15) =-12940485a(16) =-190014459a(17) =-600991549a(18) =827159379a(19) =14802832468a(20) =50584687754a(21) =-52159768068