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A145941
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Number of n X n binary arrays symmetric under 90-degree rotation with all ones connected only in a 2 X 2 elbow 1,1 1,2 2,1 in any orientation.
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0
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1, 1, 1, 1, 9, 17, 39, 147, 697, 3223, 21385, 138955, 1236361, 11421757, 147405903, 1921739323, 34678828327, 635167573009, 16140984723163, 417732159981711, 14999420093273161, 546619996126234299, 27635699247921456049
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OFFSET
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1,5
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LINKS
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EXAMPLE
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Maximal 8 X 8 example:
1 1 0 1 1 0 1 1
1 0 1 0 1 0 0 1
0 0 1 1 0 1 1 0
1 1 0 0 0 1 0 1
1 0 1 0 0 0 1 1
0 1 1 0 1 1 0 0
1 0 0 1 0 1 0 1
1 1 0 1 1 0 1 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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