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A137334
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Number of n X n crossword puzzles with dihedral symmetry group, for n odd. Acceptable crossword puzzles must have all words of length 3 or more, at least one word in each row and each column and be connected.
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1
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OFFSET
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3,2
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COMMENTS
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The number of such puzzles for an even n = 2m is equal to the number of (2m-1) X (2m-1) puzzles.
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LINKS
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EXAMPLE
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a(5) = 2 because, using 0's for white squares and 1's for black squares, the only two 5 X 5 puzzles with dihedral symmetry group are:
00000
00000
00000
00000
00000
and
10001
00000
00000
00000
10001
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Marc Brodie (mbrodie(AT)wju.edu), Apr 07 2008
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STATUS
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approved
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