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%I #10 Oct 19 2017 06:14:13
%S 0,2,5,14,40,113,320,906,2565,7262,20560,58209,164800,466578,1320965,
%T 3739886,10588280,29977297,84871040,240284954,680289285,1926019518,
%U 5452902560,15438133441,43708091520,123745352482,350345021445
%N Number of 0..2 arrays of length n with each element differing from at least one neighbor by 1 or less, starting with 0.
%C Column 2 of A221683.
%H R. H. Hardin, <a href="/A221677/b221677.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-1) +2*a(n-2) +a(n-3).
%F Empirical g.f.: x^2*(2 + x) / (1 - 2*x - 2*x^2 - x^3). - _Colin Barker_, Oct 19 2017
%e Some solutions for n=6
%e ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
%e ..1....1....1....1....1....1....1....0....1....0....1....1....1....0....0....1
%e ..2....1....0....0....1....0....2....2....2....1....2....1....2....2....1....0
%e ..0....1....0....0....1....0....2....2....0....1....0....2....1....2....0....0
%e ..1....0....2....0....2....1....2....0....0....0....0....1....2....1....1....1
%e ..0....1....2....1....2....1....1....0....1....1....0....2....1....0....0....0
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 22 2013
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