E.g.f. exp(tan(x) + sec(x) - 1).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =23a(5) =107a(6) =583a(7) =3633a(8) =25444a(9) =197620a(10) =1684295a(11) =15618141a(12) =156453857a(13) =1683050189a(14) =19344093070a(15) =236497985706