T(n, k) = [x^k] (2*n)! [z^(2*n)] 1/cos(z)^x, triangle read by rows, for 0 <= k <= n.

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =2a(5) =3a(6) =0a(7) =16a(8) =30a(9) =15a(10) =0a(11) =272a(12) =588a(13) =420a(14) =105a(15) =0a(16) =7936a(17) =18960a(18) =16380a(19) =6300a(20) =945a(21) =0a(22) =353792a(23) =911328a(24) =893640a(25) =429660a(26) =103950a(27) =10395a(28) =0a(29) =22368256