Expansion of cos x + tan x + sec x.

Terms

a(0) =2a(1) =1a(2) =0a(3) =2a(4) =6a(5) =16a(6) =60a(7) =272a(8) =1386a(9) =7936a(10) =50520a(11) =353792a(12) =2702766a(13) =22368256a(14) =199360980a(15) =1903757312a(16) =19391512146a(17) =209865342976