E.g.f. cos(x)/(cos(x)-x).

Terms

a(0) =1a(1) =1a(2) =2a(3) =9a(4) =48a(5) =325a(6) =2640a(7) =24997a(8) =270592a(9) =3295017a(10) =44582400a(11) =663532001a(12) =10773295104a(13) =189494874413