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 A194994 #8 Jul 22 2025 12:39:29 %S A194994 5,14,66,458,4990,81014,2059822,78060014,4641074078,410310652370, %T A194994 57068977108754,11768868532345686,3829513291002131546, %U A194994 1842092248483706146126,1402261360946084657783246 %N A194994 Number of lower triangles of an n X n 0..4 array with each element differing from all of its horizontal and vertical neighbors by one. %C A194994 Column 4 of A194998 %H A194994 R. H. Hardin, <a href="/A194994/b194994.txt">Table of n, a(n) for n = 1..24</a> %e A194994 Some solutions for 4X4 %e A194994 ..3........2........2........2........2........4........1........4 %e A194994 ..2.1......1.0......3.2......3.4......3.2......3.2......2.3......3.2 %e A194994 ..3.2.3....0.1.2....2.3.2....2.3.4....2.3.2....2.3.4....3.2.3....4.3.4 %e A194994 ..2.1.2.3..1.0.1.2..1.2.3.2..1.2.3.4..1.2.1.2..1.2.3.4..2.1.2.1..3.4.3.2 %K A194994 nonn %O A194994 1,1 %A A194994 _R. H. Hardin_ Sep 07 2011