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 A208305 #7 May 18 2020 19:27:22 %S A208305 1,52,21147,113503692,2475181138384,148049849095504726, %T A208305 19558496206477343793824,4971673449365938875551493054, %U A208305 2209363673053161750976745846408452,1599235210372714053663919266990430641290,1785670329039896818784300269276903576597674264 %N A208305 Number of 5 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 A208305 Andrew Howroyd, <a href="/A208305/b208305.txt">Table of n, a(n) for n = 0..100</a> %e A208305 Some solutions for n=4: %e A208305 ..0..1..0..1....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208305 ..0..1..0..1....0..1..0..1....3..0..1..0....0..1..0..1....0..2..0..1 %e A208305 ..0..1..2..0....0..1..0..1....4..0..1..0....0..1..0..1....0..1..0..1 %e A208305 ..0..1..2..0....0..1..2..0....1..2..1..0....0..2..0..1....0..2..0..1 %e A208305 ..0..1..2..3....0..1..2..0....0..2..1..4....0..1..0..1....0..1..2..0 %Y A208305 Row 5 of A208301. %K A208305 nonn %O A208305 0,2 %A A208305 _R. H. Hardin_, Feb 25 2012 %E A208305 a(0)=1 prepended and terms a(7) and beyond from _Andrew Howroyd_, May 18 2020