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.
%I A204681 #10 Jul 24 2025 19:37:31 %S A204681 12,2191,287379,40919141,5770321516,815364171994,115180678788869, %T A204681 16271532972153414,2298647402512667451,324726122304981135405, %U A204681 45873499136412060284740,6480470930161792394441041 %N A204681 Number of nX4 0..3 arrays with no occurrence of three equal elements in a row horizontally, vertically, diagonally or antidiagonally, and new values 0..3 introduced in row major order. %C A204681 Column 4 of A204685 %H A204681 Ron Hardin, <a href="/A204681/b204681.txt">Table of n, a(n) for n = 1..73</a> %e A204681 Some solutions for n=5 %e A204681 ..0..0..1..2....0..0..1..0....0..0..1..0....0..0..1..2....0..0..1..1 %e A204681 ..0..1..2..1....1..1..2..0....1..0..1..0....1..2..1..1....0..0..2..0 %e A204681 ..2..3..1..2....2..0..1..1....0..1..2..2....3..2..0..3....3..1..2..0 %e A204681 ..0..2..2..3....2..0..2..2....2..3..2..2....3..0..1..3....3..1..1..2 %e A204681 ..2..0..0..1....1..1..3..2....3..1..1..3....2..1..1..2....0..2..0..2 %K A204681 nonn %O A204681 1,1 %A A204681 _R. H. Hardin_ Jan 18 2012