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

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =19a(6) =37a(7) =52a(8) =-25a(9) =-630a(10) =-3616a(11) =-15897a(12) =-61476a(13) =-215135a(14) =-677464a(15) =-1823081a(16) =-3389900a(17) =2523349a(18) =73121734a(19) =526205851a(20) =2914005085a(21) =14163375846a(22) =62788424920a(23) =255900158756a(24) =945473736954