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%I #9 Sep 14 2018 16:11:59
%S 4,13,44,153,536,1881,6604,23189,81428,285937,1004080,3525873,
%T 12381268,43477405,152672956,536118281,1882604616,6610854857,
%U 23214328476,81518208805,286255033124,1005198043361,3529800316000,12395060210401
%N Number of n X 3 0..2 arrays with top left element 0, horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and antidiagonal differences never 0.
%H R. H. Hardin, <a href="/A229397/b229397.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + 3*a(n-3) - a(n-4).
%F Empirical g.f.: x*(4 - 7*x + 3*x^2 - x^3) / ((1 - x)*(1 - 4*x + 2*x^2 - x^3)). - _Colin Barker_, Sep 14 2018
%e Some solutions for n=4:
%e 0 0 0 0 0 2 0 2 1 0 2 2 0 2 1 0 0 2 0 0 0
%e 1 1 0 1 0 0 1 0 2 1 0 0 1 0 2 1 0 0 1 1 0
%e 2 2 1 2 1 1 2 1 0 2 1 1 1 1 0 1 1 0 2 1 0
%e 0 2 2 2 2 2 2 2 1 2 2 1 2 2 1 2 1 0 2 1 1
%Y Column 3 of A229402.
%K nonn
%O 1,1
%A _R. H. Hardin_, Sep 22 2013