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

Terms

a(0) =1a(1) =-1a(2) =0a(3) =3a(4) =4a(5) =15a(6) =54a(7) =245a(8) =1240a(9) =7119a(10) =45290a(11) =317229a(12) =2423268a(13) =20055607a(14) =178747646a(15) =1706919045a(16) =17386518448a(17) =188166282399