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%I #8 Mar 02 2018 06:26:47
%S 3,9,16,33,73,160,361,835,1966,4703,11399,27914,68903,171121,426940,
%T 1068865,2682789,6746336,16988333,42822747,108024178,272648551,
%U 688426371,1738750602,4392467427,11098043841,28043540864,70868720569,179102669081
%N Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,0,1,0,0 for x=0,1,2,3,4.
%C Every 0 is next to 0 2's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 0's, every 4 is next to 4 0's.
%C Column 2 of A197537.
%H R. H. Hardin, <a href="/A197531/b197531.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 3*a(n-1) - a(n-3) - 4*a(n-4) - 3*a(n-5) + a(n-7) + a(n-8).
%F Empirical g.f.: x*(1 + x)^2*(3 - 6*x - 2*x^2 - 2*x^3 + x^4 + 2*x^5) / ((1 - x - x^2 - x^3)*(1 - 2*x - x^2 - x^3 + x^5)). - _Colin Barker_, Mar 02 2018
%e Some solutions for n=4:
%e ..1..0....1..0....0..1....1..0....1..1....2..1....0..0....0..1....2..1....0..0
%e ..1..0....2..1....1..1....1..1....0..0....1..0....0..0....1..1....1..0....0..3
%e ..1..1....2..1....1..0....0..1....0..3....1..0....0..0....1..0....1..1....0..0
%e ..0..1....1..0....1..0....1..2....0..0....2..1....1..1....2..1....0..1....0..0
%Y Cf. A197537.
%K nonn
%O 1,1
%A _R. H. Hardin_, Oct 16 2011
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