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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.

A240887 Number of n X n 0..2 arrays with no element equal to a different number of vertical neighbors than horizontal neighbors, with new values 0..2 introduced in row major order.

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%I A240887 #7 Jul 23 2025 11:07:51
%S A240887 1,4,57,2362,245268,64074526,41971040844,69012323813116,
%T A240887 284711573170326892
%N A240887 Number of n X n 0..2 arrays with no element equal to a different number of vertical neighbors than horizontal neighbors, with new values 0..2 introduced in row major order.
%C A240887 Diagonal of A240893
%e A240887 Some solutions for n=4
%e A240887 ..0..1..2..1....0..1..0..1....0..1..0..0....0..1..0..2....0..1..0..2
%e A240887 ..2..0..1..0....1..0..2..0....1..2..0..0....2..0..1..0....1..0..2..0
%e A240887 ..0..1..2..1....0..2..1..1....0..0..1..1....0..2..0..1....2..1..0..1
%e A240887 ..1..2..1..2....2..0..1..1....0..0..1..1....2..0..1..2....0..2..1..0
%K A240887 nonn
%O A240887 1,2
%A A240887 _R. H. Hardin_, Apr 14 2014

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