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 A206691 #7 Jul 22 2025 19:36:48 %S A206691 16,1216,11264,127008,1454810,17277556,208563912,2543024548, %T A206691 31198656992,384076975680,4737250216482,58497114248288, %U A206691 722787914355820,8933909144447138,110448738176212632,1365616810440861728 %N A206691 Number of nX7 0..3 arrays with no element equal to another within two positions in the same row or column, and new values 0..3 introduced in row major order. %C A206691 Column 7 of A206692 %H A206691 R. H. Hardin, <a href="/A206691/b206691.txt">Table of n, a(n) for n = 1..210</a> %e A206691 Some solutions for n=4 %e A206691 ..0..1..2..3..0..1..2....0..1..2..3..1..0..2....0..1..2..3..0..2..3 %e A206691 ..1..3..0..1..2..3..0....1..3..0..1..2..3..0....1..2..3..0..1..3..0 %e A206691 ..2..0..1..2..3..0..1....2..0..3..2..0..1..3....2..3..1..2..3..0..1 %e A206691 ..0..2..3..0..1..2..3....3..2..1..0..3..2..1....3..1..0..3..2..1..3 %K A206691 nonn %O A206691 1,1 %A A206691 _R. H. Hardin_ Feb 11 2012