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A251143 Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to 4 and no 2 X 2 subblock having exactly two nonzero entries.

%I A251143 #15 Nov 26 2018 11:11:39
%S A251143 27,49,87,161,299,565,1075,2065,3991,7761,15163,29749,58563,115617,
%T A251143 228791,453633,900875,1791413,3566099,7105137,14166487,28262129,
%U A251143 56409627,112633781,224967459,449449345,898113015,1794954785,3587852651
%N A251143 Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to 4 and no 2 X 2 subblock having exactly two nonzero entries.
%H A251143 R. H. Hardin, <a href="/A251143/b251143.txt">Table of n, a(n) for n = 1..210</a>
%F A251143 Empirical: a(n) = 3*a(n-1) - 5*a(n-3) + a(n-4) + 2*a(n-5).
%F A251143 Empirical g.f.: x*(27 - 32*x - 60*x^2 + 35*x^3 + 34*x^4) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)). - _Colin Barker_, Nov 26 2018
%e A251143 Some solutions for n=4:
%e A251143 ..2..1..2....1..1..0....2..0..2....1..1..2....2..1..1....2..0..2....1..1..0
%e A251143 ..1..0..1....0..2..1....1..1..1....2..0..1....1..0..2....1..1..1....1..1..2
%e A251143 ..1..2..1....1..1..0....2..0..2....1..1..2....2..1..1....0..2..0....1..1..0
%e A251143 ..1..0..1....1..1..2....1..1..1....2..0..1....0..1..1....1..1..1....1..1..2
%e A251143 ..2..1..2....2..0..1....1..1..1....1..1..2....1..2..0....1..1..1....1..1..0
%Y A251143 Column 2 of A251149.
%K A251143 nonn
%O A251143 1,1
%A A251143 _R. H. Hardin_, Nov 30 2014