Euler (or secant) numbers E(n).

Terms

a(0) =1a(1) =0a(2) =-1a(3) =0a(4) =5a(5) =0a(6) =-61a(7) =0a(8) =1385a(9) =0a(10) =-50521a(11) =0a(12) =2702765a(13) =0a(14) =-199360981a(15) =0a(16) =19391512145a(17) =0a(19) =0a(21) =0a(23) =0a(25) =0a(27) =0a(29) =0