Triangle read by rows: T(n,k) = binomial(2(n-k),n-k)/(1-2(n-k)).

Terms

a(0) =1a(1) =-2a(2) =1a(3) =-2a(4) =-2a(5) =1a(6) =-4a(7) =-2a(8) =-2a(9) =1a(10) =-10a(11) =-4a(12) =-2a(13) =-2a(14) =1a(15) =-28a(16) =-10a(17) =-4a(18) =-2a(19) =-2a(20) =1a(21) =-84a(22) =-28a(23) =-10a(24) =-4a(25) =-2a(26) =-2a(27) =1a(28) =-264a(29) =-84