cp's OEIS Frontend

A252813 Number of n X n nonnegative integer arrays with upper left 0 and every value within 2 of its city block distance from the upper left and every value increasing by 0 or 1 with every step right or down.

%I A252813 #8 Jul 23 2025 13:40:04
%S A252813 1,6,63,684,7564,86724,1033761,12755742,161986236,2106102800,
%T A252813 27918827562,376114207132,5136290930902,70961672284626,
%U A252813 990271326335611,13940676825684808,197768062909075426,2824828311338844486
%N A252813 Number of n X n nonnegative integer arrays with upper left 0 and every value within 2 of its city block distance from the upper left and every value increasing by 0 or 1 with every step right or down.
%C A252813 Diagonal of A252820
%H A252813 R. H. Hardin, <a href="/A252813/b252813.txt">Table of n, a(n) for n = 1..40</a>
%e A252813 Some solutions for n=4
%e A252813 ..0..0..1..2....0..1..2..3....0..1..1..2....0..1..1..2....0..1..2..2
%e A252813 ..0..0..1..2....1..1..2..3....0..1..1..2....1..2..2..3....1..2..2..3
%e A252813 ..0..1..2..3....2..2..3..4....0..1..2..3....2..2..3..3....2..2..3..4
%e A252813 ..1..2..3..4....2..3..4..4....1..2..3..4....2..3..3..4....3..3..4..5
%K A252813 nonn
%O A252813 1,2
%A A252813 _R. H. Hardin_, Dec 22 2014