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%I #7 Jan 24 2019 11:07:06
%S 3,9,27,79,229,659,1889,5401,15419,43977,125355,357191,1017565,
%T 2898435,8255201,23510865,66956883,190683433,543031707,1546443295,
%U 4403932917,12541401683,35714999425,101707905961,289639951179,824825396777
%N Number of length-n 0..2 arrays with no repeated value differing from the previous repeated value by more than one.
%H R. H. Hardin, <a href="/A269578/b269578.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 4*a(n-1) - 2*a(n-2) - 4*a(n-3) + a(n-4).
%F Empirical g.f.: x*(3 - 3*x - 3*x^2 + x^3) / (1 - 4*x + 2*x^2 + 4*x^3 - x^4). - _Colin Barker_, Jan 24 2019
%e Some solutions for n=6:
%e ..2. .2. .0. .0. .1. .0. .1. .1. .2. .2. .2. .2. .1. .1. .2. .0
%e ..2. .1. .0. .0. .0. .0. .2. .1. .0. .1. .0. .1. .1. .0. .1. .1
%e ..0. .2. .2. .1. .2. .1. .1. .1. .2. .1. .2. .1. .1. .0. .0. .0
%e ..1. .0. .0. .1. .1. .2. .2. .0. .1. .1. .1. .1. .2. .1. .0. .0
%e ..1. .2. .0. .0. .2. .1. .0. .1. .0. .0. .2. .2. .1. .0. .0. .0
%e ..0. .2. .2. .0. .0. .1. .2. .0. .2. .0. .2. .2. .0. .2. .2. .2
%Y Column 2 of A269583.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 01 2016
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