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Search: id:A132444
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| A132444 |
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Number of n x n crossword puzzles with rotational symmetry and exactly one black square per row, up to symmetry. |
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+0
4
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OFFSET
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3,6
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COMMENT
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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. Since the puzzles counted in sequence A132443 come naturally in pairs (by reflective symmetry), the numbers in this sequence are obtained by dividing the corresponding numbers in A132443 by 2.
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EXAMPLE
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a(6) = 1 because up to symmetry, the only 6 X 6 crossword puzzle with exactly one black square in each row (using 1's for black squares and 0's for white) is:
100000
100000
100000
000001
000001
000001
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MAPLE
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See the program for A132443
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CROSSREFS
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Cf. A130578, A132443, A132445, A132446.
Sequence in context: A137254 A163481 A157805 this_sequence A111504 A041057 A041058
Adjacent sequences: A132441 A132442 A132443 this_sequence A132445 A132446 A132447
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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), Aug 21 2007
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