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%I #8 Nov 01 2018 12:24:25
%S 13,36,101,285,806,2281,6457,18280,51753,146521,414826,1174445,
%T 3325061,9413836,26652237,75457205,213632718,604832081,1712386801,
%U 4848070480,13725746641,38860021041,110019605842,311485000405,881869233533
%N Number of length n+3 0..2 arrays with no four elements in a row with pattern abab (with a!=b) and new values 0..2 introduced in 0..2 order.
%H R. H. Hardin, <a href="/A243038/b243038.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) - a(n-3) - a(n-4).
%F Empirical g.f.: x*(13 - 3*x - 7*x^2 - 5*x^3) / ((1 - x)*(1 - 2*x - 2*x^2 - x^3)). - _Colin Barker_, Nov 01 2018
%e Some solutions for n=4:
%e ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
%e ..1....1....0....0....0....1....1....1....0....1....1....0....1....1....0....1
%e ..2....2....0....1....1....2....1....1....0....1....1....1....0....2....0....2
%e ..0....0....0....1....2....0....1....0....1....2....2....1....2....0....1....1
%e ..0....1....1....0....2....1....0....1....0....1....1....1....1....2....2....0
%e ..1....0....2....1....1....2....2....2....2....0....1....2....1....1....1....1
%e ..1....2....2....2....2....0....1....1....1....1....2....2....1....0....0....1
%Y Column 2 of A243044.
%K nonn
%O 1,1
%A _R. H. Hardin_, May 29 2014
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