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Number of 3Xn arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2
1

%I #4 Jan 15 2013 06:14:59

%S 0,7,30,2110,26374,681300,11554698,239213277,4414861636,86099730502,

%T 1625526991148,31160102911062,591775127780270,11285743215972044,

%U 214648325661089776,4087126318623042490,77761170034232040294

%N Number of 3Xn arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2

%C Row 3 of A221400

%H R. H. Hardin, <a href="/A221402/b221402.txt">Table of n, a(n) for n = 1..20</a>

%e Some solutions for n=3

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Jan 15 2013