A143870 Number of ways of placing kings with no more than 1 mutual attack on an n X n chessboard.

1, 2, 11, 91, 1462, 38483, 1755113, 140404442, 19400886875, 4764856837927, 2050537030592506, 1572046460892726633, 2133798146501117397613, 5167591018292995062973870, 22288638410038000574365307819, 171813750317653145879779979300275, 2366759768251260378737273078723819964

Offset

0,2

Links

R. H. Hardin, Table of n, a(n) for n = 0..26

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

Cf. A143875, A143881, A143886.

Cf. A143871, A143872, A143873, A143874.

Diagonal of A268781.

Sequence in context: A266656 A094955 A352292 * A047854 A366402 A222080

Adjacent sequences: A143867 A143868 A143869 * A143871 A143872 A143873

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