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

Terms

a(0) =0a(1) =0a(2) =2a(3) =6a(4) =32a(5) =300a(6) =3576a(7) =52234a(8) =906688a(9) =18229176a(10) =416505760a(11) =10657541422a(12) =301871501568