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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

CROSSREFS

Sequence in context: A120872 A204771 A141512 * A319464 A019642 A248811

Adjacent sequences:  A143874 A143875 A143876 * A143878 A143879 A143880

KEYWORD

nonn,more,hard

AUTHOR

R. H. Hardin, Sep 04 2008

STATUS

approved

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Last modified May 27 04:33 EDT 2020. Contains 334649 sequences. (Running on oeis4.)