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A210903
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Number of n X n 0..2 symmetric matrices with every element equal to one, two 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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0, 1, 4, 78, 3740, 449340, 133337482, 98375439948, 180233106621896, 820210662659082911, 9270740885407976025652, 260267690197125447266436984, 18148375825241525659505646969576
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OFFSET
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1,3
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LINKS
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EXAMPLE
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Some solutions for n=4
..0..0..1..2....0..0..2..2....0..0..1..2....0..0..2..2....0..0..1..1
..0..0..1..2....0..1..1..2....0..0..1..2....0..1..1..1....0..0..1..0
..1..1..1..0....2..1..1..2....1..1..0..0....2..1..1..2....1..1..0..0
..2..2..0..0....2..2..2..2....2..2..0..0....2..1..2..2....1..0..0..0
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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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