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 A208199 #7 Jul 22 2025 21:14:31 %S A208199 187,648569,2468504665,9402035642924,35810971705853725, %T A208199 136398703432330477549,519522527116810577984260, %U A208199 1978784616446414312287693835,7536898505819261464135073030914 %N A208199 Number of nX6 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or left-upward diagonal neighbors. %C A208199 Column 6 of A208201 %H A208199 R. H. Hardin, <a href="/A208199/b208199.txt">Table of n, a(n) for n = 1..210</a> %e A208199 Some solutions for n=4 %e A208199 ..0..1..1..1..0..0....0..0..0..0..0..1....0..0..0..0..0..0....0..1..1..0..0..0 %e A208199 ..0..1..0..1..0..1....0..1..2..1..3..2....0..1..1..0..2..1....0..1..2..3..2..1 %e A208199 ..0..1..1..1..0..2....1..3..0..3..1..0....0..1..0..2..2..1....1..1..0..3..2..3 %e A208199 ..3..0..1..2..1..1....2..1..0..3..3..3....0..3..1..0..1..0....3..0..0..2..1..3 %K A208199 nonn %O A208199 1,1 %A A208199 _R. H. Hardin_ Feb 24 2012