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%I #9 Aug 04 2018 14:32:54
%S 0,4,8,81,392,2500,14112,83521,484128,2829124,16473800,96059601,
%T 559785800,3262922884,19017180288,110841719041,646029804672,
%U 3765346202500,21946028005832,127910874833361,745519107896648
%N Number of 2 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2.
%C Row 2 of A221255.
%H R. H. Hardin, <a href="/A221256/b221256.txt">Table of n, a(n) for n = 1..41</a>
%F Empirical: a(n) = 6*a(n-1) + 6*a(n-2) - 42*a(n-3) + 42*a(n-5) - 6*a(n-6) - 6*a(n-7) + a(n-8).
%F Empirical g.f.: x^2*(4 - 16*x + 9*x^2 + 26*x^3 - 2*x^4 - 6*x^5 + x^6) / ((1 - x)*(1 + x)*(1 - 6*x + x^2)*(1 + 2*x - x^2)*(1 - 2*x - x^2)). - _Colin Barker_, Aug 04 2018
%e Some solutions for n=3:
%e 0 2 2 1 2 0 0 2 1 0 2 1 0 2 0 1 2 0 1 2 1
%e 0 2 0 0 2 1 0 2 1 1 2 0 1 2 1 1 2 0 0 2 0
%Y Cf. A221255.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 06 2013
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