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A217268 Number of n X 3 arrays of occupancy after each element moves to some horizontal or vertical neighbor. 1

%I

%S 2,64,1472,33856,772800,17640000,402494400,9183772224,209543184576,

%T 4781079618624,109088244863424,2489028863068224,56791310102324928,

%U 1295787666826276416,29565538631067860928,674586660240498844224

%N Number of n X 3 arrays of occupancy after each element moves to some horizontal or vertical neighbor.

%C Column 3 of A217273.

%H R. H. Hardin, <a href="/A217268/b217268.txt">Table of n, a(n) for n = 1..28</a>

%F Empirical: a(n) = 24*a(n-1) - 648*a(n-3) + 729*a(n-4) for n>5.

%F Empirical g.f.: 2*x*(1 + 8*x - 32*x^2 - 88*x^3 + 135*x^4) / ((1 - 24*x + 27*x^2)*(1 - 27*x^2)). - _Colin Barker_, Jul 23 2018

%e Some solutions for n=3:

%e ..1..1..0....1..1..0....1..3..1....1..1..2....0..2..2....0..1..0....1..2..0

%e ..2..0..1....0..1..1....1..0..0....2..0..0....0..0..0....1..2..3....1..1..1

%e ..1..1..2....1..3..1....0..1..2....1..2..0....1..3..1....2..0..0....1..1..1

%Y Cf. A217273.

%K nonn

%O 1,1

%A _R. H. Hardin_, Sep 29 2012

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Last modified June 15 15:16 EDT 2021. Contains 345049 sequences. (Running on oeis4.)