Triangular array, see Mathematica code.

Terms

a(0) =2a(1) =1a(2) =-1a(3) =-4a(4) =2a(5) =1a(6) =4a(7) =-4a(8) =2a(9) =-1a(10) =-16a(11) =24a(12) =-16a(13) =4a(14) =1a(15) =16a(16) =-32a(17) =28a(18) =-12a(19) =3a(20) =-1a(21) =-64a(22) =160a(23) =-176a(24) =104a(25) =-36a(26) =6a(27) =1a(28) =64a(29) =-192