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 A194499 #8 Jul 22 2025 12:33:45 %S A194499 2,8,72,1020,32768,2097152,268460064,68721573888,35184372088832, %T A194499 36028797020012544 %N A194499 Number of lower triangles of an n X n 0..2 array with each element unequal to the sum mod 3 of its horizontal and vertical neighbors. %C A194499 Column 2 of A194505 %e A194499 Some solutions for 3X3 %e A194499 ..1......1......2......0......0......0......0......2......0......1......1 %e A194499 ..0.0....2.0....0.0....2.0....2.1....2.2....2.2....1.2....2.0....0.2....2.1 %e A194499 ..1.2.0..2.2.1..0.1.2..0.2.0..2.1.0..1.1.0..1.1.2..1.2.0..0.2.1..2.1.2..1.1.0 %K A194499 nonn %O A194499 1,1 %A A194499 _R. H. Hardin_ Aug 27 2011