E.g.f.: -arcsin(x)*LambertW(-x).

Terms

a(0) =0a(1) =0a(2) =2a(3) =6a(4) =40a(5) =340a(6) =3984a(7) =57050a(8) =982528a(9) =19616328a(10) =446355840a(11) =11384327438a(12) =321701896704