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%I #8 Oct 06 2018 03:53:01
%S 0,4,8,12,32,84,184,412,976,2276,5224,12076,28032,64884,150040,347324,
%T 804144,1861124,4307400,9970252,23077600,53414548,123632504,286160860,
%U 662347408,1533063972,3548423976,8213173612,19010179136,44000880564
%N Number of (n+1) X (1+1) 0..2 arrays with every element next to itself plus and minus one within the range 0..2 horizontally or antidiagonally.
%H R. H. Hardin, <a href="/A232901/b232901.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-1) - a(n-2) + 4*a(n-3).
%F Empirical g.f.: 4*x^2 / (1 - 2*x + x^2 - 4*x^3). - _Colin Barker_, Oct 06 2018
%e Some solutions for n=5:
%e ..2..1....0..1....2..1....0..1....2..1....2..1....0..1....0..1....2..1....0..1
%e ..0..2....2..0....0..2....2..2....0..0....0..0....2..1....2..1....0..2....2..1
%e ..1..0....1..2....1..0....1..0....1..2....1..2....0..0....0..1....1..0....0..1
%e ..2..1....0..1....0..1....0..1....0..1....2..1....1..2....2..1....1..2....2..0
%e ..0..2....2..2....2..0....2..2....2..2....0..2....1..0....0..0....1..0....1..2
%e ..1..0....1..0....1..2....1..0....1..0....1..0....1..2....1..2....1..2....1..0
%Y Column 1 of A232908.
%K nonn
%O 1,2
%A _R. H. Hardin_, Dec 02 2013
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