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A123818
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Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2.
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0
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1, 3, 31, 412, 6435, 106108, 1825803, 32320892, 584956651, 10772558067, 201219520632
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OFFSET
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1,2
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LINKS
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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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