Expansion of e.g.f.: (1+x)*sech(x).

Terms

a(0) =1a(1) =1a(2) =-1a(3) =-3a(4) =5a(5) =25a(6) =-61a(7) =-427a(8) =1385a(9) =12465a(10) =-50521a(11) =-555731a(12) =2702765a(13) =35135945a(14) =-199360981a(15) =-2990414715a(16) =19391512145a(17) =329655706465