Expansion of e.g.f.: tanh(x)/(1+x).

Terms

a(0) =0a(1) =1a(2) =-2a(3) =4a(4) =-16a(5) =96a(6) =-576a(7) =3760a(8) =-30080a(9) =278656a(10) =-2786560a(11) =30298368a(12) =-363580416a(13) =4748913664a(14) =-66484791296a(15) =995368112128