G.f. satisfies A(x) = 1 + x*A(x)^2 / (1 + x*A(x)^3).

Terms

a(0) =1a(1) =1a(2) =1a(3) =-1a(4) =-8a(5) =-16a(6) =16a(7) =195a(8) =491a(9) =-317a(10) =-6293a(11) =-18608a(12) =4610a(13) =230385a(14) =780625a(15) =107615a(16) =-9028280a(17) =-34695607a(18) =-17401607a(19) =367885509a(20) =1598468196a(21) =1350497961a(22) =-15317000747a(23) =-75391402496a(24) =-88375867528a(25) =643505487144