Triangle of coefficients in expansion of D^n (sec x) / sec x in powers of tan x.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =6a(6) =5a(7) =28a(8) =24a(9) =61a(10) =180a(11) =120a(12) =61a(13) =662a(14) =1320a(15) =720a(16) =1385a(17) =7266a(18) =10920a(19) =5040a(20) =1385a(21) =24568a(22) =83664a(23) =100800a(24) =40320a(25) =50521a(26) =408360a(27) =1023120a(28) =1028160a(29) =362880