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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A229438 Number of n X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing.

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%I A229438 #7 Jul 23 2025 05:45:13
%S A229438 3,7,22,109,753,6374,62205,676983,8026548,101907085,1368004992,
%T A229438 19233435438,281169127711,4249797119751,66116288446463
%N A229438 Number of n X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing.
%C A229438 Diagonal of A229445
%e A229438 Some solutions for n=4
%e A229438 ..0..2..2..2....0..2..2..2....0..2..2..2....0..0..0..0....1..1..1..1
%e A229438 ..1..0..2..2....1..0..0..2....1..0..0..2....1..1..1..1....2..2..2..2
%e A229438 ..1..1..0..0....2..1..1..0....1..1..1..0....1..1..1..1....2..2..2..2
%e A229438 ..2..1..0..0....2..1..1..1....2..1..1..0....2..2..2..2....2..2..2..2
%K A229438 nonn
%O A229438 1,1
%A A229438 _R. H. Hardin_ Sep 23 2013

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