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A146053
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Number of n X n binary arrays symmetric under 180 degree rotation with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
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0
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1, 1, 1, 5, 29, 139, 901, 5485, 74291, 1056181, 24810777, 651071773, 25748617719, 1169149922235, 81072042123257, 6590052771959131
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