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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.

A209012 Number of n X n 0..3 arrays with no element equal the average of immediate neighbors vertically above, diagonally above and left, and horizontally left of it.

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%I A209012 #8 Jul 22 2025 21:34:38
%S A209012 4,130,57412,337083370,26361689168962,27444816617702590210,
%T A209012 380386826513820237531618354,70188235698940395931354096660136964,
%U A209012 172416055686564260854366909730038107238333862
%N A209012 Number of n X n 0..3 arrays with no element equal the average of immediate neighbors vertically above, diagonally above and left, and horizontally left of it.
%C A209012 Diagonal of A209019
%e A209012 Some solutions for n=4
%e A209012 ..2..3..1..0....1..2..1..3....2..3..1..3....1..3..2..1....0..1..2..3
%e A209012 ..3..2..3..0....3..3..3..0....3..2..1..1....2..1..0..3....1..3..3..0
%e A209012 ..2..3..3..0....0..3..1..1....0..2..0..1....3..3..3..0....2..0..1..2
%e A209012 ..1..3..0..2....3..1..0..0....1..3..3..1....0..3..1..3....1..2..0..0
%K A209012 nonn
%O A209012 1,1
%A A209012 _R. H. Hardin_ Mar 04 2012

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