E.g.f.: sec(x)^3+(sec(x)^2*tan(x)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =33a(5) =136a(6) =723a(7) =3968a(8) =25953a(9) =176896a(10) =1376643a(11) =11184128a(12) =101031873a(13) =951878656a(14) =9795436563a(15) =104932671488