%I #6 May 04 2021 21:57:44
%S 6,50,435,3834,34001,302615,2699598,24121674,215786649,1932081885,
%T 17311097568,155188936431,1391839527240,12487516404434,
%U 112071578930795,1006067340461802,9033468257955009,81126883587357557,728697257578499280
%N Number of 0..2 arrays of length 2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle).
%C Row 1 of A212232.
%H R. H. Hardin, <a href="/A212233/b212233.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=3
%e ..2....1....2....1....0....1....1....0....0....0....1....0....1....1....0....0
%e ..0....0....0....0....2....0....2....2....0....2....1....1....1....0....1....2
%e ..2....2....0....1....1....2....0....0....1....1....0....2....1....1....1....0
%e ..1....1....1....1....0....0....1....2....0....0....1....2....0....0....1....0
%e ..0....0....0....1....2....1....1....1....1....2....1....1....0....1....0....1
%e ..1....0....1....1....0....1....1....0....2....1....0....0....2....2....1....1
%Y Cf. A212232.
%K nonn
%O 1,1
%A _R. H. Hardin_ May 06 2012