Expansion of e.g.f.: (1-x)^(-1-x).

Terms

a(0) =1a(1) =1a(2) =4a(3) =15a(4) =80a(5) =490a(6) =3534a(7) =28938a(8) =266048a(9) =2710440a(10) =30311640a(11) =369127440a(12) =4862219592a(13) =68881435896