O.g.f.: Sum_{n>=0} n!*(x/(1+x)^2)^n.

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =4a(5) =19a(6) =112a(7) =771a(8) =6088a(9) =54213a(10) =537392a(11) =5867925a(12) =69975308a(13) =904788263a(14) =12607819040a(15) =188341689287