E.g.f. satisfies A(x) = 1/(1 - x^2*A(x))^x.

Terms

a(0) =1a(1) =0a(2) =0a(3) =6a(4) =0a(5) =60a(6) =1080a(7) =1680a(8) =80640a(9) =1058400a(10) =8316000a(11) =257463360a(12) =3692304000a(13) =66421555200