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 A208098 #11 May 18 2020 03:01:37 %S A208098 1,5,34,1573,169064,34438557,11535531783,5804338800147, %T A208098 4121852595871393,3947133396896179889,4923290609971869799119, %U A208098 7783034938833777039389506,15253558021465456746321690675,36391805974300638618769192592189,104086634920105554145003030677202100 %N A208098 Number of 3 X n nonnegative integer arrays with new values 0 upwards introduced in row major order and no element equal to any horizontal, diagonal or antidiagonal neighbor (colorings ignoring permutations of colors). %H A208098 Andrew Howroyd, <a href="/A208098/b208098.txt">Table of n, a(n) for n = 0..100</a> %e A208098 Some solutions for n=4: %e A208098 ..0..1..0..2....0..1..0..1....0..1..2..0....0..1..0..1....0..1..0..1 %e A208098 ..3..1..0..2....0..1..0..1....0..1..2..0....0..2..3..1....0..1..0..1 %e A208098 ..0..1..0..1....2..1..2..1....0..1..2..0....0..1..0..4....0..1..0..1 %Y A208098 Row 3 of A208096. %K A208098 nonn %O A208098 0,2 %A A208098 _R. H. Hardin_, Feb 23 2012 %E A208098 a(0)=1 prepended and terms a(9) and beyond from _Andrew Howroyd_, May 17 2020