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 A194617 #9 Jun 03 2025 16:39:32 %S A194617 47,4322,132214,1674043,12561823,66369488,279618492,975189851, %T A194617 2972844263,8086809479,20111108169,46277171169,100029289052, %U A194617 204344500677,398372414831,744412292078,1341415693780,2338177034539,3960008651919 %N A194617 Half the number of lower triangles of a 4 X 4 0..n array with no element equal to the average of its horizontal and vertical neighbors. %H A194617 R. H. Hardin, <a href="/A194617/b194617.txt">Table of n, a(n) for n = 1..50</a> %e A194617 Some solutions for n=2 %e A194617 ..1........1........0........1........1........1........2........0 %e A194617 ..0.1......0.2......2.2......2.0......2.2......2.2......0.2......2.0 %e A194617 ..0.1.0....1.2.0....0.0.2....1.2.1....1.1.0....0.0.1....1.1.0....0.1.1 %e A194617 ..0.2.2.0..2.0.0.1..1.0.0.2..0.0.2.1..1.2.0.2..1.0.0.1..1.0.0.1..2.0.2.1 %Y A194617 Row 3 of A194615. %K A194617 nonn %O A194617 1,1 %A A194617 _R. H. Hardin_, Aug 30 2011