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Number of 0..2 arrays of length 2+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle)
1

%I #4 May 06 2012 19:37:50

%S 31,311,2902,26637,242780,2204646,19976155,180744711,1633768428,

%T 14757208260,133224377745,1202213897088,10845157390965,97807813761227,

%U 881892198839574,7950191559259765,71659250039164212,645816864760873772

%N Number of 0..2 arrays of length 2+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle)

%C Row 3 of A212232

%H R. H. Hardin, <a href="/A212235/b212235.txt">Table of n, a(n) for n = 1..210</a>

%e Some solutions for n=3

%e ..0....0....1....0....0....1....1....0....2....1....1....2....2....0....0....1

%e ..0....1....0....1....1....0....1....2....2....0....1....1....0....2....0....1

%e ..0....0....0....1....1....1....0....1....1....0....0....0....0....1....0....2

%e ..0....1....0....0....1....0....0....0....0....0....0....0....0....0....2....0

%e ..0....0....1....1....1....2....2....1....0....0....2....1....0....0....0....2

%e ..0....1....1....0....2....0....1....1....0....0....1....0....1....0....2....0

%e ..0....2....2....0....0....0....1....1....1....1....2....0....1....0....1....0

%e ..1....1....1....1....1....0....2....1....2....2....1....2....0....0....1....1

%K nonn

%O 1,1

%A _R. H. Hardin_ May 06 2012