Expansion of e.g.f. exp( tan x ).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =37a(6) =177a(7) =959a(8) =6097a(9) =41641a(10) =325249a(11) =2693691a(12) =24807321a(13) =241586893a(14) =2558036145a(15) =28607094455a(16) =342232522657