

A083029


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


9



1, 1, 1, 1, 3, 3, 1, 1, 6, 15, 20, 15, 6, 1, 1, 10, 45, 120, 210, 192, 200, 90, 45, 10, 1
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OFFSET

1,5


LINKS

Table of n, a(n) for n=1..25.
Index entries for sequences related to binary matrices


EXAMPLE

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


CROSSREFS

Rows sums give A085658.
A038379(n) = Sum_{k=0..C(n, 2)} 2^k*T(n, k).
A084546 is an upper bound.
Sequence in context: A144163 A080858 A144228 * A084546 A288266 A174116
Adjacent sequences: A083026 A083027 A083028 * A083030 A083031 A083032


KEYWORD

nonn,tabf,more


AUTHOR

N. J. A. Sloane, Jul 13 2003


STATUS

approved



