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 A209588 #8 Jul 22 2025 21:50:05 %S A209588 4,256,28672,51380224,161128382464,8084777718513664, %T A209588 709908161907247808512,997369854092025849117147136, %U A209588 2452157460147152961259796760100864 %N A209588 Number of n X n 0..3 arrays with every element equal to a diagonal or antidiagonal reflection. %C A209588 Column 3 of A209593 %H A209588 R. H. Hardin, <a href="/A209588/b209588.txt">Table of n, a(n) for n = 1..30</a> %F A209588 a(n) = 4 ^ (2*n-(n modulo 2)) * 28 ^ ((n*n-2*n+(n modulo 2))/4) %e A209588 Some solutions for n=3 %e A209588 ..3..0..2....2..0..1....0..2..0....3..3..1....0..3..0....0..2..3....2..3..0 %e A209588 ..0..2..1....0..1..3....2..3..2....2..0..3....1..2..3....2..0..2....3..1..3 %e A209588 ..2..1..0....3..3..2....1..2..1....3..2..3....3..1..3....0..2..1....3..3..0 %K A209588 nonn %O A209588 1,1 %A A209588 _R. H. Hardin_ Mar 10 2012