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A278686
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Number of non-equivalent ways to place 7 non-attacking ferses on an n X n board.
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5
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0, 0, 0, 27, 4860, 164423, 2651890, 25981150, 180378380, 971905679, 4316504623, 16457726539, 55463445891, 168782705327, 471407278652, 1223710587908, 2982045310010
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OFFSET
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1,4
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COMMENTS
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A fers is a leaper [1, 1].
Rotations and reflections of placements are not counted. If they are to be counted, see A201248.
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LINKS
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EXAMPLE
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There are 27 non-equivalent ways to place 7 non-attacking ferses (X) on a 4 X 4 board, rotations and reflections being ignored, e.g., these two:
XXXX X.XX
.... ....
XXX. X.X.
.... X.X.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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