E.g.f. sec(log(1+tanh(x))).

Terms

a(0) =1a(1) =0a(2) =1a(3) =-3a(4) =8a(5) =-40a(6) =256a(7) =-1568a(8) =11108a(9) =-96720a(10) =908836a(11) =-9084108a(12) =101147408a(13) =-1233325600a(14) =15998088016a(15) =-221845635248