cp's OEIS Frontend

A250806 Number of (n+1) X (2+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.

%I A250806 #9 Nov 20 2018 16:32:01
%S A250806 100,379,1315,4321,13735,42769,131455,400681,1214695,3669409,11058895,
%T A250806 33278041,100036855,300516049,902359135,2708699401,8129342215,
%U A250806 24394514689,73196520175,219615512761,658898442775,1976799137329
%N A250806 Number of (n+1) X (2+1) 0..2 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.
%H A250806 R. H. Hardin, <a href="/A250806/b250806.txt">Table of n, a(n) for n = 1..210</a>
%F A250806 Empirical: a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3); a(n) = (126*3^n - 99*2^n + 20)/2.
%F A250806 Empirical g.f.: x*(100 - 221*x + 141*x^2) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - _Colin Barker_, Nov 20 2018
%e A250806 Some solutions for n=4:
%e A250806 ..2..1..1....1..0..0....2..2..2....2..2..1....0..0..0....0..0..0....2..0..0
%e A250806 ..1..1..1....0..0..0....1..1..1....1..1..1....0..0..0....2..2..2....0..0..0
%e A250806 ..1..1..1....2..2..2....2..2..2....1..1..1....1..2..2....2..2..2....0..0..0
%e A250806 ..0..1..1....1..1..2....0..1..1....1..1..2....1..2..2....2..2..2....0..0..0
%e A250806 ..1..2..2....0..0..1....1..2..2....0..0..2....0..1..2....0..2..2....0..0..2
%Y A250806 Column 2 of A250812.
%K A250806 nonn
%O A250806 1,1
%A A250806 _R. H. Hardin_, Nov 27 2014