Expansion of log(1+log(1+x))/cosh(x).

Terms

a(0) =0a(1) =1a(2) =-2a(3) =4a(4) =-23a(5) =183a(6) =-1459a(7) =13592a(8) =-153348a(9) =1975117a(10) =-28287606a(11) =449154660a(12) =-7849907559a(13) =149555531331