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%I #9 Mar 02 2018 08:03:23
%S 0,1,1,2,3,6,11,23,47,103,226,517,1194,2830,6778,16498,40501,100420,
%T 250513,628749,1584525,4007957,10164528,25835883,65777232,167694004,
%U 427960360,1093068944,2793604179,7143313914,18272673575,46755936515
%N Number of n X 1 0..4 arrays with values 0..4 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.
%C Column 1 of A198669.
%H R. H. Hardin, <a href="/A198662/b198662.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 4*a(n-1) + a(n-2) - 17*a(n-3) + 6*a(n-4) + 21*a(n-5) - 6*a(n-6) - 8*a(n-7) for n>8.
%F Empirical g.f.: x^2*(1 - 3*x^2 - x^3)*(1 - 3*x + 3*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)*(1 - x - 4*x^2)). - _Colin Barker_, Mar 02 2018
%e All solutions for n=5:
%e ..0....0....0
%e ..0....0....0
%e ..1....0....0
%e ..1....0....1
%e ..1....0....1
%Y Cf. A198669.
%K nonn
%O 1,4
%A _R. H. Hardin_, Oct 28 2011
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