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%I #8 Nov 16 2018 17:39:28
%S 18,22,30,46,78,142,270,526,1038,2062,4110,8206,16398,32782,65550,
%T 131086,262158,524302,1048590,2097166,4194318,8388622,16777230,
%U 33554446,67108878,134217742,268435470,536870926,1073741838,2147483662,4294967310
%N Number of (n+1) X (3+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nonincreasing x(i,j)-x(i-1,j) in the j direction.
%H R. H. Hardin, <a href="/A250737/b250737.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 3*a(n-1) - 2*a(n-2); a(n) = 2^(n+1) + 14.
%F Empirical g.f.: 2*x*(9 - 16*x) / ((1 - x)*(1 - 2*x)). - _Colin Barker_, Nov 16 2018
%e Some solutions for n=4:
%e ..0..1..0..0....1..0..1..1....0..0..0..0....0..0..1..1....0..0..0..0
%e ..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0
%e ..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0
%e ..0..1..0..0....1..0..1..1....0..0..0..0....0..0..1..1....0..0..0..0
%e ..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0
%Y Column 3 of A250742.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 27 2014
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