E.g.f.: 1 / (1 - x * exp(-2*x)).

Terms

a(0) =1a(1) =1a(2) =-2a(3) =-6a(4) =40a(5) =120a(6) =-1872a(7) =-3920a(8) =155776a(9) =56448a(10) =-19946240a(11) =44799744a(12) =3588719616a(13) =-21265587200a(14) =-850126505984