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%I #4 Jun 12 2012 07:43:04
%S 6,106,1758,28722,466136,7536790,121573668,1957953138,31497261096,
%T 506264941416,8132104116670,130559338628190,2095252193645448,
%U 33614011364219588,539119053140521448,8644670545679274098
%N Number of 0..3 arrays of length 2*n with sum less than 3*n in any length 2n subsequence (=less than 50% duty cycle)
%C Row 1 of A213464
%H R. H. Hardin, <a href="/A213465/b213465.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=3
%e ..0....1....2....1....2....1....0....1....3....0....2....1....3....0....3....2
%e ..2....2....1....2....0....1....2....1....2....2....0....2....0....1....0....0
%e ..0....1....1....0....0....1....1....0....1....3....2....3....1....3....1....0
%e ..0....1....1....1....1....2....0....2....0....1....3....1....0....0....3....1
%e ..0....2....1....2....0....0....3....2....1....2....0....1....0....2....0....2
%e ..2....1....0....0....3....3....0....2....0....0....0....0....1....2....0....1
%K nonn
%O 1,1
%A _R. H. Hardin_ Jun 12 2012