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A195798
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Number of triangular n X n X n 0..1 arrays with all rows and diagonals having the same length having the same sum, with corners zero.
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1
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1, 1, 2, 8, 16, 64, 1184, 5300, 130324, 14748808, 421963232, 54990266540
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OFFSET
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1,3
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COMMENTS
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For n <= 6, all solutions are rotationally symmetric, which implies that a(n) = 2^(A007997(n+4)-1). But for n >= 7 there exist asymmetric solutions like
0
0 0
0 0 1
0 1 0 0
1 0 0 0 0
0 0 0 0 1 0
0 0 0 1 0 0 0.
(End)
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LINKS
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EXAMPLE
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Some solutions for n=5
......0..........0..........0..........0..........0..........0..........0
.....0.0........0.0........0.0........0.1........0.1........0.1........0.1
....0.1.0......1.0.1......1.1.1......0.0.0......0.1.0......1.0.1......1.1.1
...0.1.1.0....0.0.0.0....0.1.1.0....1.0.0.0....1.1.1.0....1.0.0.0....1.1.1.0
..0.0.0.0.0..0.0.1.0.0..0.0.1.0.0..0.0.0.1.0..0.0.0.1.0..0.0.1.1.0..0.0.1.1.0
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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