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 A211914 #6 Jun 02 2025 07:51:54 %S A211914 0,0,10,1492,227388,9345480,172044141,1908272916,14931819099 %N A211914 Number of lower triangular n X n arrays colored with integers 0 upwards introduced in row major order, with no element equal to any horizontal, vertical, diagonal or antidiagonal neighbor, and containing the value n(n+1)/2-5. %C A211914 Column 4 of A211916 %e A211914 Some solutions for n=4 %e A211914 ..0........0........0........0........0........0........0........0 %e A211914 ..1.2......1.2......1.2......1.2......1.2......1.2......1.2......1.2 %e A211914 ..3.0.4....3.4.0....3.4.3....3.4.5....0.3.4....0.3.1....3.4.0....3.0.4 %e A211914 ..1.5.3.1..5.1.6.4..5.6.5.1..0.6.0.6..5.6.5.2..2.4.0.5..1.5.6.5..1.2.1.5 %K A211914 nonn %O A211914 1,3 %A A211914 _R. H. Hardin_ Apr 25 2012