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A143870 Number of ways of placing kings with no more than 1 mutual attack on an n X n chessboard. 6
1, 2, 11, 91, 1462, 38483, 1755113, 140404442, 19400886875, 4764856837927, 2050537030592506, 1572046460892726633, 2133798146501117397613, 5167591018292995062973870, 22288638410038000574365307819, 171813750317653145879779979300275, 2366759768251260378737273078723819964 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
EXAMPLE
Configurations of 0,1,2,3 or 4 kings on an 2 X 2 chessboard and the number of mutual attacks:
.. .. .. K. .K .. K. KK .K .K K. K. .K KK KK KK
.. K. .K .. .. KK K. .. .K K. .K KK KK .K K. KK
0 0 0 0 0 1 1 1 1 1 1 3 3 3 3 6
From 16 configurations is 11 with no more than 1 mutual attack, a(2)=11.
CROSSREFS
Diagonal of A268781.
Sequence in context: A266656 A094955 A352292 * A047854 A366402 A222080
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 04 2008
EXTENSIONS
Example added by Vaclav Kotesovec, Oct 20 2014
Additional terms from R. H. Hardin, Feb 13 2016
STATUS
approved

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Last modified April 14 12:23 EDT 2024. Contains 371661 sequences. (Running on oeis4.)