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 A206859 #7 Jul 22 2025 19:43:56 %S A206859 69,4761,192575,7598355,314918295,13093461017,541018725304, %T A206859 22336434688428,923097673638406,38158725414249736,1577142038208976046, %U A206859 65180147142970134040,2693823565225042593429,111334863067931222656792 %N A206859 Number of nX4 0..2 arrays avoiding the pattern z z+1 z in any row, column, diagonal or antidiagonal. %C A206859 Column 4 of A206863 %H A206859 R. H. Hardin, <a href="/A206859/b206859.txt">Table of n, a(n) for n = 1..210</a> %e A206859 Some solutions for n=4 %e A206859 ..0..1..2..2....1..2..2..2....0..2..2..0....0..2..0..1....1..1..1..0 %e A206859 ..2..2..0..0....1..2..2..2....1..0..0..0....2..0..1..1....1..2..2..2 %e A206859 ..0..2..2..0....1..2..2..1....2..2..1..2....0..2..1..1....0..2..2..2 %e A206859 ..0..1..1..1....1..2..2..1....0..1..2..2....2..0..0..1....2..0..0..1 %K A206859 nonn %O A206859 1,1 %A A206859 _R. H. Hardin_ Feb 13 2012