A080858 Triangle read by rows: T(n,k), n >=1, 0 <= k <= C(n,k), = number of n X n symmetric positive definite matrices with 2's on the main diagonal and 1's and 0's elsewhere and with k 1's above the diagonal.

1, 1, 1, 1, 3, 3, 1, 1, 6, 15, 20, 12, 6, 1, 1, 10, 45, 120, 190, 192, 140, 80, 30, 10, 1, 1, 15, 105, 455, 1290, 2382, 3385, 3195, 2880, 1860, 1098, 435, 240, 60, 15, 1, 1, 21, 210, 1330, 5775, 17157, 36092, 60210, 75075, 87185, 68775, 64470, 38395, 26355, 13125, 7987, 2394, 1365, 560, 105, 21, 1, 1, 28, 378, 3276, 19985, 86772, 265286, 595136, 1104642, 1499680, 2036412, 2057496, 2115855, 1729672, 1508580, 912128, 755300, 378336, 260848, 120120, 80388, 26384, 16856, 4200, 3640, 840, 168, 28, 1

Offset: 1

Author

N. J. A. Sloane, Jul 13 2003

Keywords

• nonn
• tabf

Examples

			1;
1,1;
1,3,3,1;
1,6,15,20,12,6,1;
...
		

Links

• Index entries for sequences related to binary matrices

Crossrefs

Rows sums give A085657.

A085656(n) = Sum_{k=0..C(n,2)} 2^k * T(n,k).

Extensions

Rows n=6..8 added by Max Alekseyev, Jun 04 2024