A238518 - OEIS

%I #8 Oct 24 2018 08:26:21

%S 84,588,7056,74676,812028,8777664,95006100,1028017452,11124397872,

%T 120377861940,1302620868444,14095781346528,152531780288916,

%U 1650560738719116,17860873095687888,193274188450247604

%N Number of (n+1) X (1+1) 0..3 arrays with no element equal to all horizontal neighbors or equal to all vertical neighbors.

%H R. H. Hardin, <a href="/A238518/b238518.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 9*a(n-1) + 21*a(n-2) - 14*a(n-3).

%F Empirical g.f.: 84*x*(1 - 2*x) / (1 - 9*x - 21*x^2 + 14*x^3). - _Colin Barker_, Oct 24 2018

%e Some solutions for n=4:

%e ..3..1....1..2....2..1....3..2....3..1....2..0....2..3....2..3....3..0....0..3

%e ..2..3....0..1....0..3....1..0....1..3....3..2....3..2....1..0....1..3....2..0

%e ..0..3....0..3....2..3....3..1....3..0....0..3....1..2....2..0....2..1....1..3

%e ..0..2....1..0....1..2....1..3....1..0....3..2....0..1....1..2....3..0....2..0

%e ..1..0....0..1....3..0....2..0....3..2....2..3....2..3....3..1....0..3....1..3

%Y Column 1 of A238523.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 28 2014