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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.

A205155 Number of n X n 0..3 arrays with no occurrence of three equal elements in a row horizontally, vertically or nw-to-se diagonally, and new values 0..3 introduced in row major order.

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%I A205155 #9 Jul 22 2025 18:35:13
%S A205155 1,15,6941,54314298,4826926610498,4948963310952700521
%N A205155 Number of n X n 0..3 arrays with no occurrence of three equal elements in a row horizontally, vertically or nw-to-se diagonally, and new values 0..3 introduced in row major order.
%C A205155 Diagonal of A205161
%e A205155 Some solutions for n=5
%e A205155 ..0..0..1..0..0....0..0..1..0..1....0..0..1..0..0....0..1..0..0..1
%e A205155 ..2..1..3..2..2....0..2..2..1..0....1..1..2..3..3....1..1..2..2..3
%e A205155 ..2..2..3..2..2....3..1..0..1..0....3..2..0..0..2....3..0..3..3..0
%e A205155 ..3..1..1..3..1....0..0..1..2..1....1..1..3..1..0....0..3..3..0..2
%e A205155 ..1..2..1..3..2....3..3..0..2..0....0..1..0..2..3....1..0..1..0..1
%K A205155 nonn
%O A205155 1,2
%A A205155 _R. H. Hardin_ Jan 22 2012

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