Triangle read by rows: let p(n, x) = x*p(n-1, x) - p(n-2, x), then T(n, x) = d^2/dx^2 (p(n, x)).

Terms

a(0) =2a(1) =-2a(2) =6a(3) =-6a(4) =-6a(5) =12a(6) =6a(7) =-24a(8) =-12a(9) =20a(10) =12a(11) =24a(12) =-60a(13) =-20a(14) =30a(15) =-12a(16) =60a(17) =60a(18) =-120a(19) =-30a(20) =42a(21) =-20a(22) =-60a(23) =180a(24) =120a(25) =-210a(26) =-42a(27) =56a(28) =20a(29) =-120