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 A209678 #10 Jul 22 2025 21:53:30 %S A209678 1,14,608,246038,166075313,1008907523438,10215188674804688, %T A209678 930859067991577148438,141374220951220779418945313, %U A209678 193240888262699902868270874023438 %N A209678 Number of n X n 0..3 arrays with every element equal to a diagonal or antidiagonal reflection, and new values 0 upwards introduced in row major order. %C A209678 Column 2 of A209684 %H A209678 R. H. Hardin, <a href="/A209678/b209678.txt">Table of n, a(n) for n = 1..42</a> %e A209678 Some.solutions.for.n=3 %e A209678 ..0..0..1....0..0..1....0..1..2....0..0..1....0..1..2....0..1..2....0..0..1 %e A209678 ..0..0..0....0..2..0....2..1..1....0..0..2....1..1..1....0..1..1....0..1..1 %e A209678 ..1..0..0....2..0..1....1..2..0....0..2..0....0..1..0....0..0..0....2..1..1 %K A209678 nonn %O A209678 1,2 %A A209678 _R. H. Hardin_ Mar 11 2012