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%I #9 Jun 20 2022 21:29:37
%S 20,68,148,380,740,1724,3220,7196,13220,28988,52948,115100,210020,
%T 454844,830740,1796636,3286820
%N Number of (n+1) X (n+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).
%F Empirical: a(n) = a(n-1) +9*a(n-2) -9*a(n-3) -26*a(n-4) +26*a(n-5) +24*a(n-6) -24*a(n-7).
%e Some solutions for n=4:
%e 2 0 3 0 1 1 3 1 3 2 2 0 2 1 2 0 2 1 2 0
%e 1 3 2 3 0 2 0 2 0 3 0 2 0 3 0 2 0 3 0 2
%e 2 0 3 0 1 0 2 0 2 1 3 1 3 2 3 1 3 2 3 1
%e 1 3 2 3 0 2 0 2 0 3 0 2 0 3 0 2 0 3 0 2
%e 2 0 3 0 1 0 2 0 2 1 3 1 3 2 3 0 2 1 2 0
%Y Diagonal of A235289.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jan 05 2014