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A235281
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Number of (n+1) X (n+1) 0..3 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 4 (constant-stress 1 X 1 tilings).
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0
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20, 68, 148, 380, 740, 1724, 3220, 7196, 13220, 28988, 52948, 115100, 210020, 454844, 830740, 1796636, 3286820
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) +9*a(n-2) -9*a(n-3) -26*a(n-4) +26*a(n-5) +24*a(n-6) -24*a(n-7).
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EXAMPLE
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Some solutions for n=4:
2 0 3 0 1 1 3 1 3 2 2 0 2 1 2 0 2 1 2 0
1 3 2 3 0 2 0 2 0 3 0 2 0 3 0 2 0 3 0 2
2 0 3 0 1 0 2 0 2 1 3 1 3 2 3 1 3 2 3 1
1 3 2 3 0 2 0 2 0 3 0 2 0 3 0 2 0 3 0 2
2 0 3 0 1 0 2 0 2 1 3 1 3 2 3 0 2 1 2 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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