Irregular triangle read by rows: row n is the expansion of (1 + 2*x - x^2)^n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =-1a(4) =1a(5) =4a(6) =2a(7) =-4a(8) =1a(9) =1a(10) =6a(11) =9a(12) =-4a(13) =-9a(14) =6a(15) =-1a(16) =1a(17) =8a(18) =20a(19) =8a(20) =-26a(21) =-8a(22) =20a(23) =-8a(24) =1a(25) =1a(26) =10a(27) =35a(28) =40a(29) =-30