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A210909
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Number of n X n 0..2 symmetric matrices with every element equal to zero, one or three horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
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0
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1, 2, 24, 616, 34972, 4448872, 1271872472, 816403740024, 1175380974129748, 3797950184579806600, 27543816778839681854992, 448288796291335397449297608
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OFFSET
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1,2
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LINKS
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EXAMPLE
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Some solutions for n=4
..0..1..1..2....0..1..0..1....0..1..1..1....0..1..0..2....0..1..2..0
..1..0..2..0....1..1..1..2....1..2..1..2....1..1..1..2....1..0..2..1
..1..2..2..2....0..1..0..1....1..1..0..2....0..1..2..0....2..2..1..0
..2..0..2..0....1..2..1..2....1..2..2..1....2..2..0..1....0..1..0..1
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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