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A183476 Number of n X 2 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.

%I A183476 #9 Mar 29 2018 08:49:13
%S A183476 3,15,39,135,495,1647,5751,20223,70119,244863,855927,2985903,10426887,
%T A183476 36416223,127148535,444006927,1550518119,5414352255,18907098327,
%U A183476 66024403695,230558764743,805118884191,2811503074743,9817858453455
%N A183476 Number of n X 2 0..2 arrays with every element equal to either the sum mod 3 of its vertical neighbors or the sum mod 3 of its horizontal neighbors.
%C A183476 Column 2 of A183483.
%H A183476 R. H. Hardin, <a href="/A183476/b183476.txt">Table of n, a(n) for n = 1..200</a>
%F A183476 Empirical: a(n) = 3*a(n-1) + 12*a(n-3) - 18*a(n-4) - 36*a(n-6).
%F A183476 Empirical g.f.: 3*x*(1 + 2*x - 2*x^2 - 6*x^3 - 12*x^4 - 12*x^5) / ((1 - 6*x^3)*(1 - 3*x - 6*x^3)). - _Colin Barker_, Mar 29 2018
%e A183476 Some solutions for 4 X 2.
%e A183476 ..2..2....2..2....1..1....0..0....2..2....0..0....0..0....2..2....0..0....1..1
%e A183476 ..0..0....2..2....0..2....0..0....1..1....1..1....2..0....0..0....2..2....1..1
%e A183476 ..1..1....0..0....2..1....1..1....0..0....1..1....2..0....2..2....1..1....2..2
%e A183476 ..0..0....1..1....2..2....0..0....2..2....1..1....0..0....2..2....1..1....0..0
%Y A183476 Cf. A183483.
%K A183476 nonn
%O A183476 1,1
%A A183476 _R. H. Hardin_, Jan 05 2011