A113680 Riordan array ((1-x-2x^2)/(1-x),x).

1, 0, 1, -2, 0, 1, -2, -2, 0, 1, -2, -2, -2, 0, 1, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 0, 1, -2, -2, -2, -2, -2, -2, -2, -2

Offset: 0

Author

Paul Barry, Nov 04 2005

Keywords

• easy
• sign
• tabl

Comments

Inverse of A113678. Sequence array of A113679. Row sums are 3-2n-2*0^n. Diagonal sums are 1-n.

Examples

			Triangle begins
1;
0, 1;
-2, 0, 1;
-2, -2, 0, 1;
-2, -2, -2, 0, 1;
-2, -2, -2, -2, 0, 1;
		

Formula

Number triangle T(n, k)=if(k<=n, C(0, n-k)+2*C(1, n-k)-2, 0).