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%I #9 Aug 05 2018 08:20:45
%S 1,9,42,217,1116,5722,29383,150821,774219,3974308,20401353,104726538,
%T 537593996,2759637891,14166083083,72718928341,373288968420,
%U 1916208848267,9836498426064,50493818235236,259200537583569,1330557304472777
%N Number of n X 2 arrays of occupancy after each element moves to some horizontal or vertical neighbor, without consecutive moves in the same direction.
%C Column 2 of A221429.
%H R. H. Hardin, <a href="/A221425/b221425.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 4*a(n-1) + 6*a(n-2) - 5*a(n-4) + a(n-5).
%F Empirical g.f.: x*(1 + 5*x - 5*x^3 + x^4) / (1 - 4*x - 6*x^2 + 5*x^4 - x^5). - _Colin Barker_, Aug 05 2018
%e Some solutions for n=3:
%e ..0..1....2..0....1..1....0..1....1..2....2..0....1..0....1..1....1..1....2..1
%e ..1..1....2..1....1..1....2..2....0..0....1..0....3..2....2..1....0..0....1..0
%e ..2..1....0..1....1..1....1..0....2..1....1..2....0..0....1..0....2..2....1..1
%Y Cf. A221429.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 15 2013
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