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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.

A208871 Number of nX7 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

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%I A208871 #7 Jul 22 2025 21:32:49
%S A208871 715,4578580,32271626438,228847686794351,1624001903270517563,
%T A208871 11525604443642285224422,81798476241280856702695038,
%U A208871 580533377647449287012352167379,4120113916814898485216382089787455
%N A208871 Number of nX7 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.
%C A208871 Column 7 of A208872
%H A208871 R. H. Hardin, <a href="/A208871/b208871.txt">Table of n, a(n) for n = 1..210</a>
%e A208871 Some solutions for n=4
%e A208871 ..0..0..0..0..0..0..0....0..1..1..2..0..1..0....0..0..0..0..1..2..1
%e A208871 ..1..2..1..1..1..1..1....0..0..0..3..0..1..1....1..1..1..2..1..3..3
%e A208871 ..1..0..3..2..2..2..3....2..1..2..2..1..0..3....2..2..0..2..2..1..2
%e A208871 ..3..0..3..3..3..0..1....2..3..0..2..3..0..0....0..1..1..0..2..3..0
%K A208871 nonn
%O A208871 1,1
%A A208871 _R. H. Hardin_ Mar 02 2012

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