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 A207866 #7 Mar 11 2023 20:14:36 %S A207866 5,500,278982,455546040,1625686993918,10764437129618296, %T A207866 119010390034543491042,2040368351234509987725212, %U A207866 51350903376256822436382238230,1818472780230512625778385363238944,87604972777997602798029710458933219862,5585379463993456459896660751935863285859008 %N A207866 Number of n X 4 nonnegative integer arrays with new values 0 upwards introduced in row major order and no element equal to any horizontal or vertical neighbor (colorings ignoring permutations of colors). %H A207866 Andrew Howroyd, <a href="/A207866/b207866.txt">Table of n, a(n) for n = 1..140</a> %e A207866 Some solutions for n=5 %e A207866 ..0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1 %e A207866 ..1..0..1..0....1..0..1..0....1..2..3..2....1..0..1..0....1..2..1..0 %e A207866 ..0..1..0..1....0..1..2..1....0..1..0..1....0..1..2..1....0..1..0..1 %e A207866 ..1..2..1..0....1..0..1..0....1..0..1..0....1..0..1..0....1..2..1..0 %e A207866 ..0..1..0..1....0..1..3..1....0..1..0..1....0..1..0..1....0..1..2..1 %Y A207866 Column 4 of A207868. %K A207866 nonn %O A207866 1,1 %A A207866 _R. H. Hardin_, Feb 21 2012 %E A207866 Terms a(11) and beyond from _Andrew Howroyd_, Mar 11 2023