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Number of nX4 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, without 2-loops or left turns
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%I #7 May 23 2013 07:06:38

%S 0,3,5,16,41,105,288,735,1981,5156,13685,35973,94940,250271,659721,

%T 1739740,4585933,12092245,31878636,84050611,221594145,584232168,

%U 1540316025

%N Number of nX4 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, without 2-loops or left turns

%C Column 4 of A221787

%F Empirical: a(n) = 5*a(n-2) + 5*a(n-3) + a(n-5). - _Vaclav Kotesovec_, May 23 2013

%e All solutions for n=3

%e ..0..2..2..1....0..1..1..1....0..2..2..1....0..2..1..1....0..2..2..1

%e ..0..2..2..0....0..2..2..0....0..2..1..0....0..1..2..0....0..1..1..0

%e ..1..1..1..0....1..2..2..0....1..1..2..0....1..2..2..0....1..2..2..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Jan 25 2013