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 A208307 #7 May 18 2020 19:25:19 %S A208307 1,877,27644437,27700815674032,196551307092757144384, %T A208307 5737167377815628378510929822,510275358863420934339418249390485008, %U A208307 114130286115375064054502412158789812265958284,56140177561453730943968268473396800731088097525712216 %N A208307 Number of 7 X n nonnegative integer arrays with new values 0 upwards introduced in row major order and no element equal to any horizontal or antidiagonal neighbor (colorings ignoring permutations of colors). %H A208307 Andrew Howroyd, <a href="/A208307/b208307.txt">Table of n, a(n) for n = 0..50</a> %e A208307 Some solutions for n=4: %e A208307 ..0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1 %e A208307 ..0..1..0..1....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208307 ..0..1..0..1....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208307 ..2..1..0..1....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208307 ..0..1..2..0....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208307 ..0..1..2..1....2..1..0..1....0..1..2..0....0..1..0..1....0..2..0..1 %e A208307 ..0..1..0..1....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %Y A208307 Row 7 of A208301. %K A208307 nonn %O A208307 0,2 %A A208307 _R. H. Hardin_ Feb 25 2012 %E A208307 a(0)=1 prepended and terms a(6) and beyond from _Andrew Howroyd_, May 18 2020