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A143877
Number of ways of placing kings with no more than 2 mutual attacks on an n X n chessboard symmetric under horizontal and vertical reflection.
1
1, 2, 1, 7, 4, 55, 17, 576, 129, 13243, 1554, 465675, 35443, 32233206, 1330673, 3746034675, 92945020
OFFSET
0,2
CROSSREFS
Sequence in context: A120872 A204771 A141512 * A319464 A019642 A339000
KEYWORD
nonn,more,hard
AUTHOR
R. H. Hardin, Sep 04 2008
STATUS
approved