A143870 - OEIS

%I #15 Feb 13 2016 10:09:01

%S 1,2,11,91,1462,38483,1755113,140404442,19400886875,4764856837927,

%T 2050537030592506,1572046460892726633,2133798146501117397613,

%U 5167591018292995062973870,22288638410038000574365307819,171813750317653145879779979300275,2366759768251260378737273078723819964

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

%H R. H. Hardin, <a href="/A143870/b143870.txt">Table of n, a(n) for n = 0..26</a>

%e Configurations of 0,1,2,3 or 4 kings on an 2 X 2 chessboard and the number of mutual attacks:

%e .. .. .. K. .K .. K. KK .K .K K. K. .K KK KK KK

%e .. K. .K .. .. KK K. .. .K K. .K KK KK .K K. KK

%e 0  0  0  0  0  1  1  1  1  1  1  3  3  3  3  6

%e From 16 configurations is 11 with no more than 1 mutual attack, a(2)=11.

%Y Cf. A143875, A143881, A143886.

%Y Cf. A143871, A143872, A143873, A143874.

%Y Diagonal of A268781.

%K nonn

%O 0,2

%A _R. H. Hardin_, Sep 04 2008

%E Example added by _Vaclav Kotesovec_, Oct 20 2014

%E Additional terms from _R. H. Hardin_, Feb 13 2016