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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.

A185827 Half the number of n X n binary arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.

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%I A185827 #10 Jul 22 2025 10:02:42
%S A185827 0,3,30,514,15782,923808,91052720,17200095426,5976334149476,
%T A185827 3829861209246738
%N A185827 Half the number of n X n binary arrays with every element equal to exactly one or two of its horizontal and vertical neighbors.
%C A185827 Diagonal of A185835
%e A185827 Some solutions for 4X4 with a(1,1)=0
%e A185827 ..0..0..1..1....0..0..1..1....0..0..0..1....0..1..1..1....0..0..1..1
%e A185827 ..1..1..0..1....0..1..0..1....1..1..0..1....0..1..0..0....0..1..0..0
%e A185827 ..0..0..0..1....0..1..0..1....0..1..0..1....0..1..1..0....1..1..0..1
%e A185827 ..0..1..1..1....0..1..0..0....0..0..1..1....0..0..1..0....0..0..1..1
%K A185827 nonn
%O A185827 1,2
%A A185827 _R. H. Hardin_ Feb 05 2011

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