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%I #8 Nov 22 2018 11:34:15
%S 5518,27686,131982,600070,2633198,11264166,47315662,196169030,
%T 805653678,3286063846,13335635342,53918745990,217407726958,
%U 874837394726,3514985555022,14106883178950,56568421653038,226696485544806
%N Number of (n+1) X (7+1) 0..3 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing x(i,j)+x(i-1,j) in the j direction.
%H R. H. Hardin, <a href="/A250876/b250876.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 10*a(n-1) - 35*a(n-2) + 50*a(n-3) - 24*a(n-4); a(n) = (9952*4^n - 9828*3^n + 3024*2^n + 182)/3.
%F Empirical g.f.: 2*x*(2759 - 13747*x + 24126*x^2 - 13320*x^3) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)). - _Colin Barker_, Nov 22 2018
%e Some solutions for n=3:
%e ..3..3..3..3..3..3..3..3....2..3..3..3..3..3..3..3....1..1..1..1..0..0..0..0
%e ..0..2..2..2..2..2..2..2....2..3..3..3..3..3..3..3....0..0..0..0..1..1..1..1
%e ..0..2..2..2..2..3..3..3....0..2..2..2..2..2..2..2....0..0..0..0..1..1..1..1
%e ..0..2..2..2..2..3..3..3....0..2..2..2..2..2..3..3....0..0..0..2..3..3..3..3
%Y Column 7 of A250877.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 28 2014
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