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 A209589 #8 Jul 22 2025 21:50:12 %S A209589 5,625,140625,791015625,8009033203125,2027286529541015625, %T A209589 923682425022125244140625,10521320122517645359039306640625, %U A209589 215719941636994597502052783966064453125 %N A209589 Number of n X n 0..4 arrays with every element equal to a diagonal or antidiagonal reflection. %C A209589 Column 4 of A209593 %H A209589 R. H. Hardin, <a href="/A209589/b209589.txt">Table of n, a(n) for n = 1..30</a> %F A209589 a(n) = 5 ^ (2*n-(n modulo 2)) * 45 ^ ((n*n-2*n+(n modulo 2))/4) %e A209589 Some solutions for n=3 %e A209589 ..0..1..0....2..2..3....2..3..1....1..4..0....2..2..2....0..3..3....1..1..3 %e A209589 ..1..2..2....1..2..2....3..2..2....4..2..0....2..1..4....4..0..3....1..3..3 %e A209589 ..4..2..2....4..1..3....3..2..4....1..0..1....1..4..2....4..4..0....1..3..1 %K A209589 nonn %O A209589 1,1 %A A209589 _R. H. Hardin_ Mar 10 2012