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%I #11 Feb 07 2019 15:24:16
%S 0,0,1,615,84910,8241540,759337545,73117894428,7578889491370,
%T 848729993032718,102072779621746876,13069744040275286234,
%U 1766655687081261435255,250232365919081938956865,36910187948533534644694094
%N Number of n X n nonnegative integer arrays with upper left 0 and lower right n+n-6 and value increasing by 0 or 1 with every step right or down.
%H Alois P. Heinz, <a href="/A252923/b252923.txt">Table of n, a(n) for n = 1..20</a> (first 15 terms from R. H. Hardin)
%e Some solutions for n=4
%e ..0..0..1..1....0..0..1..1....0..1..1..1....0..0..1..2....0..0..0..1
%e ..0..0..1..2....0..0..1..2....0..1..2..2....0..1..1..2....0..0..1..2
%e ..0..1..2..2....1..1..1..2....0..1..2..2....1..1..1..2....0..1..2..2
%e ..1..1..2..2....1..2..2..2....1..1..2..2....1..1..1..2....1..2..2..2
%Y Diagonal of A252930.
%K nonn
%O 1,4
%A _R. H. Hardin_, Dec 24 2014