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%I #12 Jun 18 2022 23:37:52
%S 40,68,104,188,304,572,968,1868,3280,6428,11624,22988,42544,84572,
%T 159368,317708,607120,1212188,2341544,4678988,9113584,18218972,
%U 35712968,71409548,140660560,281288348,556133864,1112202188,2205141424,4410151772
%N Number of (n+1) X (2+1) 0..3 arrays with every 2 X 2 subblock having its diagonal sum differing from its antidiagonal sum by 4 (constant-stress 1 X 1 tilings).
%H R. H. Hardin, <a href="/A235283/b235283.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) + 3*a(n-2) - 15*a(n-3) + 4*a(n-4) + 18*a(n-5) - 12*a(n-6).
%F Empirical g.f.: 4*x*(10 - 13*x - 55*x^2 + 68*x^3 + 72*x^4 - 84*x^5) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)*(1 - 3*x^2)). - _Colin Barker_, Oct 18 2018
%e Some solutions for n=4:
%e 0 1 0 3 2 3 0 1 0 1 3 2 0 1 0 0 2 0 0 3 0
%e 3 0 3 0 3 0 3 0 3 2 0 3 3 0 3 3 1 3 2 1 2
%e 2 3 2 3 2 3 1 2 1 0 2 1 0 1 0 0 2 0 0 3 0
%e 3 0 3 0 3 0 3 0 3 2 0 3 3 0 3 3 1 3 1 0 1
%e 2 3 2 2 1 2 0 1 0 0 2 1 1 2 1 0 2 0 0 3 0
%Y Column 2 of A235289.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jan 05 2014
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