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A135589 Triangle T(n,k) read by rows: number of k X k symmetric (0,1)-matrices with exactly n entries equal to 1 and no zero rows or columns. 3
1, 0, 1, 0, 0, 2, 0, 0, 2, 4, 0, 0, 1, 9, 10, 0, 0, 0, 12, 36, 26, 0, 0, 0, 10, 76, 140, 76, 0, 0, 0, 6, 116, 420, 540, 232, 0, 0, 0, 3, 138, 915, 2160, 2142, 764, 0, 0, 0, 1, 136, 1605, 6230, 10766, 8624, 2620, 0, 0, 0, 0, 116, 2372, 14436, 39130, 53312, 35856, 9496, 0, 0, 0, 0 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,6

LINKS

Table of n, a(n) for n=0..69.

EXAMPLE

1

0,1

0,0,2

0,0,2,4

0,0,1,9,10

0,0,0,12,36,26

0,0,0,10,76,140,76

0,0,0,6,116,420,540,232

CROSSREFS

Main diagonal gives A000085.

Sequence in context: A134312 A195581 A020474 * A244312 A158122 A028641

Adjacent sequences:  A135586 A135587 A135588 * A135590 A135591 A135592

KEYWORD

nonn,tabl

AUTHOR

Vladeta Jovovic, Feb 25 2008

STATUS

approved

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Last modified February 23 03:41 EST 2018. Contains 299473 sequences. (Running on oeis4.)