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 A195228 #8 Jul 22 2025 12:41:19 %S A195228 5,29,337,7705,348849,31374671,5618308863,2006626824777, %T A195228 1431393426377379,2041526404394580503,5826929219460553056125, %U A195228 33306813274969071019847237,381509343842237775318179191165,8761682347863104757428803661222769 %N A195228 Number of lower triangles of an n X n 0..4 array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by one or less. %C A195228 Column 4 of A195232 %H A195228 R. H. Hardin, <a href="/A195228/b195228.txt">Table of n, a(n) for n = 1..16</a> %e A195228 Some solutions for n=4 %e A195228 ..1........1........2........2........3........0........3........1 %e A195228 ..2.1......2.1......1.2......1.1......3.2......0.0......4.4......1.2 %e A195228 ..1.2.2....1.1.1....2.1.2....1.1.0....2.2.2....0.1.0....4.4.3....2.2.2 %e A195228 ..1.1.2.3..1.0.1.2..1.2.1.2..1.0.1.1..2.2.3.2..0.1.1.1..4.4.4.3..1.1.2.2 %K A195228 nonn %O A195228 1,1 %A A195228 _R. H. Hardin_ Sep 13 2011