Expansion of (1+x)/cos(x).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =5a(5) =25a(6) =61a(7) =427a(8) =1385a(9) =12465a(10) =50521a(11) =555731a(12) =2702765a(13) =35135945a(14) =199360981a(15) =2990414715a(16) =19391512145a(17) =329655706465