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

Terms

a(0) =1a(1) =-1a(2) =0a(3) =2a(4) =-4a(5) =4a(6) =0a(7) =-8a(8) =16a(9) =-16a(10) =0a(11) =32a(12) =-64a(13) =64a(14) =0a(15) =-128a(16) =256a(17) =-256a(18) =0a(19) =512a(20) =-1024a(21) =1024a(22) =0a(23) =-2048a(24) =4096a(25) =-4096a(26) =0a(27) =8192a(28) =-16384a(29) =16384