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

Terms

a(0) =1a(1) =-1a(2) =0a(3) =0a(4) =4a(5) =-12a(6) =56a(7) =-280a(8) =1744a(9) =-11536a(10) =86208a(11) =-703296a(12) =6199744a(13) =-59653440a(14) =608357504a(15) =-6715007104a(16) =77889982720a(17) =-967972497664