%I
%S 1,4,10,26,68,178,472,1276,3462,9496,26024,71956,198740,552814,
%T 1535556,4290252,11968194,33553214,93917400,264020106,741024426,
%U 2087799972,5872999754,16577458520,46720454112,132081262316,372843051320
%N Number of 2..2 arrays x(0..n1) of n elements with zero sum and elements alternately strictly increasing and strictly decreasing
%C Column 2 of A200057
%H R. H. Hardin, <a href="/A200051/b200051.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=6
%e .1...1....0....2....0....0....0....0....0...2....0....0....1...1...2...2
%e ..1...2...1....1....1...1....1....1...1....1....2...2....2....1....1....1
%e ..0....2....0....2...2....2...2...1....1...1...2....0...2....0....0...1
%e ..2...2...1...2....0...2....1....0....0....1....0...1....2....1....1....1
%e .2....2....2...1...1....1...2...2....1....0...1....2...2...1...2...1
%e ..0....1....0...2....2....0....2....2...1....1....1....1...1....0....2....2
%K nonn
%O 1,2
%A _R. H. Hardin_ Nov 13 2011
