%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