E.g.f. (exp(x) - 1)/cos(x).

Terms

a(0) =1a(1) =1a(2) =4a(3) =7a(4) =36a(5) =91a(6) =624a(7) =2087a(8) =18256a(9) =76231a(10) =814144a(11) =4078867a(12) =51475776a(13) =300870571a(14) =4381112064a(15) =29265244847a(16) =482962852096