E.g.f.: tan(log(1+tan(x))).

Terms

a(0) =0a(1) =1a(2) =-1a(3) =6a(4) =-26a(5) =206a(6) =-1666a(7) =17476a(8) =-201256a(9) =2686856a(10) =-39501256a(11) =644639696a(12) =-11460605936a(13) =221416107056