A111965 Riordan array (1/sqrt(1-6x+5x^2),x/(1-6x+5x^2)).

1, 3, 1, 11, 6, 1, 45, 31, 9, 1, 195, 156, 60, 12, 1, 873, 781, 360, 98, 15, 1, 3989, 3906, 2055, 684, 145, 18, 1, 18483, 19531, 11403, 4395, 1155, 201, 21, 1, 86515, 97656, 62132, 26856, 8260, 1800, 266, 24, 1, 408105, 488281, 334260, 158692, 55188, 14190

Offset: 0

Author

Paul Barry, Aug 23 2005

Keywords

• easy
• nonn
• tabl

Comments

Row sums are A111966. Factors as (1/(1-x),x/(1-x))*(1/sqrt(1-4x),x/sqrt(1-4x)).

Examples

			1;
3,1;
11,6,1;
45,31,9,1;
195,156,60,12,1;
873,781,360,98,15,1;
		

Formula

Number triangle T(n, k)=sum{j=0..n, C((k+2j-1)/2, j)C(j, n-j-k)(-6)^(k-n+2j)5^(n-k-j)}