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

Terms

a(0) =1a(1) =2a(2) =-4a(3) =20a(4) =-120a(5) =800a(6) =-5696a(7) =42416a(8) =-326304a(9) =2572992a(10) =-20685696a(11) =168920704a(12) =-1397257472a(13) =11682707712a(14) =-98578346496a(15) =838369268480