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

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =25a(5) =108a(6) =525a(7) =2841a(8) =16926a(9) =109795a(10) =768721a(11) =5769848a(12) =46170841a(13) =392042257a(14) =3517885530a(15) =33240220095a(16) =329703176361