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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.

A230657 Number of n X n 0..2 black square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j).

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%I A230657 #9 Jun 02 2025 08:44:20
%S A230657 1,3,15,123,8613,337977,169006665,40860127671,131515599970167,
%T A230657 201844710508818147,4141132208926170478473,40464088148356899296269059
%N A230657 Number of n X n 0..2 black square subarrays x(i,j) with each element diagonally or antidiagonally next to at least one element with value 2-x(i,j).
%C A230657 Diagonal of A230661
%e A230657 Some solutions for n=5
%e A230657 ..x..1..x..1..x....x..2..x..0..x....x..1..x..1..x....x..1..x..1..x
%e A230657 ..1..x..1..x..1....0..x..1..x..2....1..x..0..x..1....1..x..2..x..1
%e A230657 ..x..2..x..2..x....x..1..x..0..x....x..2..x..1..x....x..0..x..0..x
%e A230657 ..0..x..1..x..0....2..x..2..x..1....2..x..1..x..2....2..x..0..x..2
%e A230657 ..x..2..x..1..x....x..0..x..1..x....x..0..x..0..x....x..2..x..0..x
%K A230657 nonn
%O A230657 1,2
%A A230657 _R. H. Hardin_, Oct 27 2013

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