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A143890 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about both diagonal and antidiagonal. 2
1, 2, 3, 9, 16, 61, 143, 802, 2265, 17236, 59156, 631443, 2686969, 39237301, 210001256 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..14.

CROSSREFS

Sequence in context: A289452 A086771 A156066 * A270339 A272057 A056658

Adjacent sequences:  A143887 A143888 A143889 * A143891 A143892 A143893

KEYWORD

nonn,more,hard

AUTHOR

R. H. Hardin, Sep 04 2008

STATUS

approved

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Last modified November 22 08:46 EST 2019. Contains 329389 sequences. (Running on oeis4.)