Triangle T(n,k) of arctangent numbers: expansion of arctan(x)^n/n!.

Terms

a(0) =1a(1) =1a(2) =-2a(3) =1a(4) =-8a(5) =1a(6) =24a(7) =-20a(8) =1a(9) =184a(10) =-40a(11) =1a(12) =-720a(13) =784a(14) =-70a(15) =1a(16) =-8448a(17) =2464a(18) =-112a(19) =1a(20) =40320a(21) =-52352a(22) =6384a(23) =-168a(24) =1a(25) =648576a(26) =-229760a(27) =14448a(28) =-240a(29) =1