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 A266237 #25 May 31 2024 10:53:48 %S A266237 1,0,1,220,68826306,739745383235859818 %N A266237 Number of magic squares of order n composed of the numbers from 1 to n^2, counted up to rotations, reflections, and M-transformations. %C A266237 Chebrakov (2008) defines M-transformations of a magic square to be simultaneous permutations of its rows/columns that preserve the content of each diagonal (i.e., M-transformations can only shuffle the diagonal elements). The number of M-transformations of a magic square of order n equals A000165(floor(n/2)) = 2*A002866(floor(n/2)). Half of the M-transformations can be obtained from the other half by rotations by 180 degrees (or by reflections about a diagonal). %C A266237 Obviously, there is no magic square for n=2, although the MATLAB command magic(n) returns a non-magic square with determinant -10. - _Altug Alkan_, Dec 25 2015 %H A266237 Yu. V. Chebrakov, <a href="http://chebrakov.narod.ru/bbb-3.1.pdf">Section 3.1.2</a> and <a href="http://chebrakov.narod.ru/bbb-3.2.pdf">Section 3.2.2</a> in "Theory of Magic Matrices. Issue TMM-1.", 2008. (in Russian) %H A266237 Hidetoshi Mino, <a href="https://magicsquare6.net/">The number of magic squares of order 6</a>. %F A266237 a(n) = A006052(n) / A002866(floor(n/2)). %Y A266237 Cf. A006052. %K A266237 nonn,hard,more %O A266237 1,4 %A A266237 _Max Alekseyev_, Dec 25 2015 %E A266237 a(6) from _Hidetoshi Mino_, Jul 22 2023 %E A266237 a(6) corrected by _Hidetoshi Mino_, May 31 2024