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A067210
Number of n X n 0..2 matrices with all row and column sums equal.
1
1, 3, 9, 87, 5673, 2577513, 8459809773, 207495141083975, 39125696231091082665, 57899300601363050181107733, 683382115404724657577266518831159, 65156055488094891194179319045960728827635, 50704966066306827486637758645370695372532720829085
OFFSET
0,2
EXAMPLE
Some solutions for n=4
..1..1..0..1....0..0..2..1....2..0..1..1....2..0..2..2....2..1..1..0
..0..2..1..0....1..1..1..0....0..1..2..1....1..2..1..2....0..2..0..2
..2..0..0..1....2..0..0..1....2..1..0..1....1..2..2..1....1..0..2..1
..0..0..2..1....0..2..0..1....0..2..1..1....2..2..1..1....1..1..1..1
CROSSREFS
Column k=2 of A202784.
Sequence in context: A203559 A184098 A249789 * A018654 A003225 A203104
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 20 2002
EXTENSIONS
a(7) and example from R. H. Hardin, Jan 05 2012
a(8)-a(12) from Andrew Howroyd, Jun 01 2017
a(0)=1 prepended by Andrew Howroyd, Oct 14 2024
STATUS
approved