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 A208301 #11 Mar 13 2023 13:31:13 %S A208301 1,1,2,2,5,5,5,42,52,15,15,602,2906,877,52,52,12840,373780,433252, %T A208301 21147,203,203,373780,87852626,656404264,113503692,678570,877,877, %U A208301 14050312,33093356640,2227156082842,2475181138384,46538017584,27644437,4140 %N A208301 T(n,k)=Number of n X k 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 A208301 Andrew Howroyd, <a href="/A208301/b208301.txt">Table of n, a(n) for n = 1..210</a> (terms 1..58 from R. H. Hardin) %e A208301 Table starts %e A208301 ....1..........1.................2.....................5 %e A208301 ....2..........5................42...................602 %e A208301 ....5.........52..............2906................373780 %e A208301 ...15........877............433252.............656404264 %e A208301 ...52......21147.........113503692.........2475181138384 %e A208301 ..203.....678570.......46538017584.....17131843186425504 %e A208301 ..877...27644437....27700815674032.196551307092757144384 %e A208301 .4140.1382958545.22702140562948192 %e A208301 Some solutions for n=4 k=3 %e A208301 ..0..1..0....0..1..0....0..1..0....0..1..0....0..1..0....0..1..2....0..1..0 %e A208301 ..0..1..0....0..1..0....0..1..0....0..1..0....2..3..0....0..3..0....0..1..0 %e A208301 ..0..1..0....0..2..1....0..1..0....0..1..0....0..2..0....0..1..0....2..1..0 %e A208301 ..0..2..1....0..2..0....0..1..0....0..1..2....0..1..0....0..3..0....2..1..2 %Y A208301 Columns 1..6 are A000110, A099977(n-1), A208297, A208298, A208299, A208300 %Y A208301 Rows 1..7 are A000110(n-1), A208302, A208303, A208305, A208305, A208306, A208307. %Y A208301 Main diagonal is A361450. %Y A208301 Cf. A207868. %K A208301 nonn,tabl %O A208301 1,3 %A A208301 _R. H. Hardin_, Feb 25 2012