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A183304 Half the number of n X 3 binary arrays with no element equal to a strict majority of its horizontal and vertical neighbors.

%I A183304 #10 Jan 27 2025 10:34:45
%S A183304 1,4,9,19,42,93,205,452,997,2199,4850,10697,23593,52036,114769,253131,
%T A183304 558298,1231365,2715861,5990020,13211405,29138671,64267362,141746129,
%U A183304 312630929,689529220,1520804569,3354240067,7398009354,16316823277
%N A183304 Half the number of n X 3 binary arrays with no element equal to a strict majority of its horizontal and vertical neighbors.
%H A183304 R. H. Hardin, <a href="/A183304/b183304.txt">Table of n, a(n) for n = 1..200</a>
%F A183304 Empirical: a(n) = 2*a(n-1)+a(n-3).
%F A183304 Empirical G.f.: x*(1+x)^2/(1-2*x-x^3). - _Colin Barker_, Feb 23 2012
%e A183304 Some solutions with a(1,1)=0 for 3X4
%e A183304 ..0..1..0..1....0..0..1..1....0..1..0..1....0..1..0..0....0..1..1..0
%e A183304 ..1..0..0..1....1..1..0..0....0..1..1..0....1..0..1..1....1..0..0..1
%e A183304 ..0..1..1..0....0..1..0..1....1..0..1..0....0..1..0..0....0..1..1..0
%Y A183304 Column 3 of A183312.
%K A183304 nonn
%O A183304 1,2
%A A183304 _R. H. Hardin_, Jan 03 2011