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A143885
Number of ways of placing kings with no more than 3 mutual attacks on an n X n chessboard symmetric under 180 degree rotation.
1
1, 2, 3, 15, 52, 383, 2273, 28764, 295391, 6544311, 116636234
OFFSET
0,2
CROSSREFS
Sequence in context: A203432 A298409 A151369 * A172012 A323709 A338308
KEYWORD
nonn,more,hard
AUTHOR
R. H. Hardin, Sep 04 2008
STATUS
approved