A109970 Riordan array (1,x(1-x)^2).

1, 0, 1, 0, -2, 1, 0, 1, -4, 1, 0, 0, 6, -6, 1, 0, 0, -4, 15, -8, 1, 0, 0, 1, -20, 28, -10, 1, 0, 0, 0, 15, -56, 45, -12, 1, 0, 0, 0, -6, 70, -120, 66, -14, 1, 0, 0, 0, 1, -56, 210, -220, 91, -16, 1, 0, 0, 0, 0, 28, -252, 495, -364, 120, -18, 1

Offset: 0

Author

Paul Barry, Jul 06 2005

Keywords

• easy
• sign
• tabl

Comments

Row sums are A077954. Diagonal sums are (-1)^n*A094686(n). Matrix inverse is A109971.

Examples

			Rows begin
1;
0,1;
0,-2,1;
0,1,-4,1;
0,0,6,-6,1;
0,0,-4,15,-8,1;
0,0,1,-20,28,-10,1;
0,0,0,15,-56,45,-12,1;
		

Formula

G.f.: 1/(1-xy(1-x)^2); Number triangle T(n, k)=binomial(2k, n-k)*(-1)^(n-k).