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 A197888 #7 Jun 02 2025 05:13:01 %S A197888 3,78,529,10827,92843,1134527,13253562,145351090,1728849664, %T A197888 19259087568,227927217325,2573394846501,29961925871053, %U A197888 341720932452731,3939440439598059,45203853693284547,520558824415292051 %N A197888 Number of nX7 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,2,1,1,1 for x=0,1,2,3,4. %C A197888 Every 0 is next to 0 0's, every 1 is next to 1 2's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's %C A197888 Column 7 of A197889 %H A197888 R. H. Hardin, <a href="/A197888/b197888.txt">Table of n, a(n) for n = 1..63</a> %e A197888 Some solutions containing all values 0 to 4 for n=4 %e A197888 ..1..0..2..1..0..1..2....0..1..2..2..1..3..1....1..2..2..1..0..1..2 %e A197888 ..2..1..1..0..2..1..1....1..3..1..1..4..1..2....0..1..1..3..2..1..1 %e A197888 ..2..1..4..1..1..0..1....2..2..1..1..1..1..2....2..1..0..1..1..4..1 %e A197888 ..1..3..1..2..0..1..2....1..1..1..2..2..1..1....1..0..1..2..0..1..2 %K A197888 nonn %O A197888 1,1 %A A197888 _R. H. Hardin_ Oct 19 2011