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A185405 1/7 the number of n X 2 0..6 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

%I A185405 #11 Apr 15 2018 08:38:36
%S A185405 1,13,150,1848,22656,278832,3430776,42221928,519611520,6394769688,
%T A185405 78699293256,968538893952,11919644165496,146693048343528,
%U A185405 1805326578739200,22217849450044248,273431322619829256
%N A185405 1/7 the number of n X 2 0..6 arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.
%C A185405 Column 2 of A185409.
%H A185405 R. H. Hardin, <a href="/A185405/b185405.txt">Table of n, a(n) for n = 1..200</a>
%F A185405 Empirical: a(n) = 11*a(n-1) + 23*a(n-2) - 72*a(n-3) - 144*a(n-4) - 216*a(n-5).
%F A185405 Empirical g.f.: x*(1 + 2*x - 16*x^2 - 29*x^3 - 42*x^4) / (1 - 11*x - 23*x^2 + 72*x^3 + 144*x^4 + 216*x^5). - _Colin Barker_, Apr 15 2018
%e A185405 Some solutions for 3 X 2 with a(1,1)=0:
%e A185405 ..0..0....0..0....0..0....0..0....0..0....0..2....0..3....0..0....0..0....0..0
%e A185405 ..2..5....2..2....5..1....6..6....2..2....0..2....0..3....0..6....0..1....6..5
%e A185405 ..2..5....5..5....5..1....5..5....4..4....3..3....3..3....6..6....0..1....6..5
%Y A185405 Cf. A185409.
%K A185405 nonn
%O A185405 1,2
%A A185405 _R. H. Hardin_, Jan 26 2011