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 A194997 #8 Jul 22 2025 12:39:50 %S A194997 8,26,138,1104,13754,261324,7686580,346018484,24069199390, %T A194997 2566345975600,422456182660436,106689940668487188, %U A194997 41576384767924321080,24871115264481653525780,22948996533081051784100632 %N A194997 Number of lower triangles of an n X n 0..7 array with each element differing from all of its horizontal and vertical neighbors by one. %C A194997 Column 7 of A194998 %H A194997 R. H. Hardin, <a href="/A194997/b194997.txt">Table of n, a(n) for n = 1..22</a> %e A194997 Some solutions for 4X4 %e A194997 ..2........6........2........2........2........0........2........2 %e A194997 ..3.2......7.6......3.4......3.2......3.2......1.0......3.2......1.2 %e A194997 ..2.1.0....6.5.6....2.3.2....2.1.0....2.3.2....2.1.0....2.3.2....2.3.2 %e A194997 ..1.0.1.0..5.6.7.6..3.4.3.2..1.2.1.0..1.2.1.0..1.2.1.0..3.4.3.2..3.4.3.4 %K A194997 nonn %O A194997 1,1 %A A194997 _R. H. Hardin_ Sep 07 2011