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A245864 Number of length n+2 0..2 arrays with some pair in every consecutive three terms totalling exactly 2.

%I A245864 #11 Nov 03 2018 13:28:17
%S A245864 19,45,103,239,553,1281,2967,6873,15921,36881,85435,197911,458463,
%T A245864 1062035,2460217,5699123,13202089,30582803,70845443,164114349,
%U A245864 380172929,880675315,2040095313,4725906149,10947620333,25360298571,58747446847
%N A245864 Number of length n+2 0..2 arrays with some pair in every consecutive three terms totalling exactly 2.
%H A245864 R. H. Hardin, <a href="/A245864/b245864.txt">Table of n, a(n) for n = 1..210</a>
%F A245864 Empirical: a(n) = 2*a(n-1) + a(n-2) - a(n-4) - a(n-5).
%F A245864 Empirical g.f.: x*(19 + 7*x - 6*x^2 - 12*x^3 - 9*x^4) / ((1 - x)*(1 - x - 2*x^2 - 2*x^3 - x^4)). - _Colin Barker_, Nov 03 2018
%e A245864 Some solutions for n=10:
%e A245864 ..1....2....1....2....0....1....0....1....0....0....2....0....0....2....0....0
%e A245864 ..1....1....1....2....0....1....2....1....2....1....2....1....0....1....1....1
%e A245864 ..1....1....1....0....2....1....1....1....0....1....0....2....2....0....1....1
%e A245864 ..1....0....0....2....1....1....1....1....2....2....2....0....0....2....2....0
%e A245864 ..1....2....2....0....1....1....1....2....2....0....1....2....2....2....0....1
%e A245864 ..0....2....0....1....2....2....0....1....0....1....1....0....1....0....2....2
%e A245864 ..2....0....1....1....0....1....2....0....2....1....0....2....1....2....2....0
%e A245864 ..2....1....1....1....2....0....0....2....2....1....1....1....1....2....0....1
%e A245864 ..0....2....2....1....0....1....0....1....0....1....1....1....0....0....0....1
%e A245864 ..2....1....1....0....1....2....2....1....1....1....1....0....1....0....2....0
%e A245864 ..2....0....0....1....1....1....0....2....2....2....1....2....1....2....2....1
%e A245864 ..0....1....1....1....1....0....2....1....0....1....1....0....2....0....0....2
%Y A245864 Column 2 of A245869.
%K A245864 nonn
%O A245864 1,1
%A A245864 _R. H. Hardin_, Aug 04 2014