A080858 - OEIS

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

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OFFSET

1,5

LINKS

Table of n, a(n) for n=1..92.

Index entries for sequences related to binary matrices

EXAMPLE

1,1;

1,3,3,1;

1,6,15,20,12,6,1;

...

CROSSREFS