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%I #8 Oct 05 2018 11:41:56
%S 4,4,8,16,28,52,96,176,324,596,1096,2016,3708,6820,12544,23072,42436,
%T 78052,143560,264048,485660,893268,1642976,3021904,5558148,10223028,
%U 18803080,34584256,63610364,116997700,215192320,395800384,727990404
%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, diagonally or antidiagonally, with no adjacent elements equal.
%H R. H. Hardin, <a href="/A232508/b232508.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n-1) + a(n-2) + a(n-3).
%F Empirical g.f.: 4*x / (1 - x - x^2 - x^3). - _Colin Barker_, Oct 05 2018
%e Some solutions for n=7:
%e ..1..0....0..1....1..0....1..0....0..1....2..1....0..1....1..0....0..1....0..1
%e ..1..2....2..1....1..2....1..2....2..1....0..1....2..1....1..2....2..1....2..1
%e ..1..0....2..1....1..0....1..0....2..0....0..1....2..1....1..2....0..1....0..1
%e ..1..2....0..1....1..2....1..2....1..0....2..1....0..1....1..0....2..1....0..2
%e ..1..0....2..1....1..0....1..2....1..2....0..1....0..1....1..0....2..1....1..2
%e ..1..2....0..1....1..2....1..0....1..2....0..1....2..1....1..2....0..1....1..0
%e ..1..2....0..1....1..0....1..0....1..0....2..1....0..1....1..0....2..1....1..0
%e ..1..0....2..1....1..2....1..2....1..2....0..1....2..1....1..2....0..1....1..2
%Y Column 1 of A232515.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 25 2013
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