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 A195226 #9 Jul 22 2025 12:41:04 %S A195226 3,15,155,3151,127785,10322065,1663418313,535153390177, %T A195226 343932423395227,441776066934784687,1134608168927438377475, %U A195226 5828490619001307113164495,59904949456032239303490933489,1232191818850202836476827846621041 %N A195226 Number of lower triangles of an n X n 0..2 array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by one or less. %C A195226 Column 2 of A195232 %H A195226 R. H. Hardin, <a href="/A195226/b195226.txt">Table of n, a(n) for n = 1..20</a> %e A195226 Some solutions for n=4 %e A195226 ..2........1........1........1........2........2........0........2 %e A195226 ..1.1......1.2......1.1......1.2......1.1......1.1......0.0......1.1 %e A195226 ..0.1.1....1.1.2....1.1.1....1.2.2....1.1.0....0.1.1....1.0.1....0.0.0 %e A195226 ..0.1.1.0..1.1.1.2..0.1.0.0..1.1.2.2..1.1.0.0..0.0.1.1..1.0.0.0..1.1.0.0 %K A195226 nonn %O A195226 1,1 %A A195226 _R. H. Hardin_ Sep 13 2011