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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.

A193609 Number of n X n symmetric 0..2 arrays with no element equal to the sum mod 3 of all its horizontal and vertical neighbors.

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%I A193609 #8 Jul 22 2025 12:26:49
%S A193609 2,6,64,1026,32832,2097152,268435456,68719348224,35184372089856,
%T A193609 36028797018963968,73786976297388343296
%N A193609 Number of n X n symmetric 0..2 arrays with no element equal to the sum mod 3 of all its horizontal and vertical neighbors.
%e A193609 Some solutions for 4X4
%e A193609 ..0..2..2..0....2..0..2..2....1..0..1..1....2..2..0..0....1..1..0..2
%e A193609 ..2..2..1..2....0..0..1..2....0..2..2..1....2..1..2..2....1..2..1..1
%e A193609 ..2..1..2..2....2..1..1..0....1..2..2..0....0..2..1..2....0..1..0..0
%e A193609 ..0..2..2..0....2..2..0..1....1..1..0..1....0..2..2..0....2..1..0..1
%K A193609 nonn
%O A193609 1,1
%A A193609 _R. H. Hardin_ Jul 31 2011

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