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 A208470 #6 Jul 22 2025 21:23:14 %S A208470 52,115975,1366230232,51074630353994,4585512913250157737, %T A208470 838156242834826375910795 %N A208470 Number of 5Xn nonnegative integer arrays with new values 0 upwards introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors. %C A208470 Row 5 of A208466 %e A208470 Some solutions for n=4 %e A208470 ..0..1..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0 %e A208470 ..0..0..1..0....0..1..0..0....0..1..0..0....0..1..1..0....0..1..0..0 %e A208470 ..0..0..0..0....0..1..0..0....2..0..1..0....0..0..0..0....0..0..1..0 %e A208470 ..0..2..0..0....0..1..0..0....0..0..0..0....0..1..0..0....0..0..1..0 %e A208470 ..0..0..1..0....0..0..1..0....0..1..0..0....0..1..0..0....0..0..0..0 %K A208470 nonn %O A208470 1,1 %A A208470 _R. H. Hardin_ Feb 27 2012