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A268973 Number of 3 X n 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once.

%I A268973 #8 Jan 17 2019 17:20:34
%S A268973 27,336,2016,11664,63792,339480,1770048,9084744,46050480,231090264,
%T A268973 1150053408,5683587048,27921925008,136471932792,664055030016,
%U A268973 3218568401160,15545839096944,74855120204952,359437016141280
%N A268973 Number of 3 X n 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once.
%H A268973 R. H. Hardin, <a href="/A268973/b268973.txt">Table of n, a(n) for n = 1..210</a>
%F A268973 Empirical: a(n) = 10*a(n-1) - 29*a(n-2) + 20*a(n-3) - 4*a(n-4) for n>6.
%F A268973 Empirical g.f.: 3*x*(9 + 22*x - 187*x^2 + 236*x^3 - 332*x^4 + 280*x^5) / (1 - 5*x + 2*x^2)^2. - _Colin Barker_, Jan 17 2019
%e A268973 Some solutions for n=4:
%e A268973 ..1..2..1..0. .2..2..2..2. .1..2..2..2. .2..1..2..2. .0..1..2..2
%e A268973 ..1..2..0..1. .2..2..1..0. .1..2..2..1. .0..0..1..2. .0..1..2..1
%e A268973 ..1..0..0..0. .1..2..1..2. .0..1..0..0. .1..2..1..0. .0..1..2..1
%Y A268973 Row 3 of A268971.
%K A268973 nonn
%O A268973 1,1
%A A268973 _R. H. Hardin_, Feb 16 2016