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A143878 Number of ways of placing kings with no more than 2 mutual attacks on an n X n chessboard symmetric about main diagonal. 1
1, 2, 5, 17, 92, 581, 4989, 54250, 776877, 14503255, 356467268, 11553201879, 495106836021 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..12.

CROSSREFS

Sequence in context: A026822 A059248 A203006 * A081546 A103511 A254132

Adjacent sequences:  A143875 A143876 A143877 * A143879 A143880 A143881

KEYWORD

nonn,more,hard

AUTHOR

R. H. Hardin, Sep 04 2008

STATUS

approved

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Last modified February 24 11:27 EST 2020. Contains 332209 sequences. (Running on oeis4.)