G.f.: Sum_{n>=0} x^n/((1+x)^(2*n)*(1 - (2*n)*x)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =13a(5) =51a(6) =234a(7) =1205a(8) =6861a(9) =42696a(10) =287893a(11) =2088343a(12) =16195822a(13) =133582909a(14) =1166593665a(15) =10746339324a(16) =104072482781