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A200045 Number T(n,m) of ways of 4-coloring an n X m grid so that there is no rectangle with all 4 corners the same color. 3

%I

%S 4,16,252,64,3912,228984,256,59928,12870096,2545607472,1024,906912,

%T 696448224,465659203104,272454472598400,4096,13571712,36376835616,

%U 79102304162784,140221913588582784

%N Number T(n,m) of ways of 4-coloring an n X m grid so that there is no rectangle with all 4 corners the same color.

%C The rectangles have sides parallel to the x- and y-axes.

%H J. D. Davies, <a href="http://www.jasondavies.com/17x17/">Number of unique rectangle-free 4-colourings for an nxm grid</a>

%e Triangle starts:

%e 4;

%e 16, 252;

%e 64, 3912, 228984;

%e 256, 59928, 12870096, 2545607472;

%e 1024, 906912, 696448224, 465659203104, 272454472598400;

%e ...

%Y Cf. A252778, A252780, A252839.

%K nonn,tabl,more

%O 1,1

%A _Jason Davies_, Nov 14 2011

%E T(6,5) from _Jason Davies_, Nov 08 2012

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Last modified May 25 00:34 EDT 2015. Contains 257801 sequences.