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

Terms

a(0) =0a(1) =1a(2) =2a(3) =0a(4) =-8a(5) =0a(6) =96a(7) =0a(8) =-2176a(9) =0a(10) =79360a(11) =0a(12) =-4245504a(13) =0a(14) =313155584a(15) =0a(16) =-30460116992a(17) =0a(19) =0a(21) =0a(23) =0a(25) =0a(27) =0a(29) =0a(31) =0