%I #8 Apr 16 2018 09:47:25

%S 64,13500,2842560,598507920,126017211780,26533211918040,

%T 5586628402633500,1176277376648694960,247667889663690066720,

%U 52147040135402715629580,10979678466093753927519840,2311796391622216326875508300

%N 1/4 the number of n X 4 0..3 arrays with no element equal both to the element above and to the element to its left.

%C Column 4 of A185567.

%H R. H. Hardin, <a href="/A185562/b185562.txt">Table of n, a(n) for n = 1..200</a>

%F Empirical: a(n) = 217*a(n-1) - 1371*a(n-2) + 2835*a(n-3) - 2025*a(n-4).

%F Empirical g.f.: 4*x*(16 - 97*x + 201*x^2 - 135*x^3) / (1 - 217*x + 1371*x^2 - 2835*x^3 + 2025*x^4). - _Colin Barker_, Apr 16 2018

%e Some solutions for 3 X 4 with a(1,1)=0:

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

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

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

%Y Cf. A185567.

%K nonn

%O 1,1

%A _R. H. Hardin_, Jan 31 2011