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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.

A199648 Number of n X n 0..2 arrays with values 0..2 introduced in row major order and each element equal to no more than two horizontal and vertical neighbors.

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%I A199648 #8 Jul 22 2025 13:21:35
%S A199648 1,14,2584,3695683,39209840355,3083761998081891,
%T A199648 1797997097480559332224,7771716024559573445914487875
%N A199648 Number of n X n 0..2 arrays with values 0..2 introduced in row major order and each element equal to no more than two horizontal and vertical neighbors.
%C A199648 Diagonal of A199655
%e A199648 Some solutions for n=3
%e A199648 ..0..1..0....0..0..1....0..1..2....0..0..1....0..1..0....0..1..1....0..0..0
%e A199648 ..0..0..1....1..0..2....0..1..2....2..2..2....2..0..0....1..2..2....0..1..1
%e A199648 ..2..0..1....2..1..0....1..1..0....1..1..2....2..0..1....1..2..1....0..1..0
%K A199648 nonn
%O A199648 1,2
%A A199648 _R. H. Hardin_ Nov 08 2011

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