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 A111485 #7 Feb 16 2025 08:32:58 %S A111485 1,3,12,107,951,10923 %N A111485 Number of (-1,0,1) periodic irreducible matrices up to sign change, transposition and mirroring over the antidiagonal. %C A111485 "Irreducible" is intended to mean "not factoring into blocks along the diagonal". The periods for n=6 are 396 times period 3, 2939 times period 4, 1684 times period 6 and 5904 times period 12. %H A111485 Wouter Meeussen, <a href="http://users.pandora.be/Wouter.Meeussen/PseudoAntiSymmetricMatrixPowers.nb">Periodic</a> %H A111485 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PeriodicMatrix.html">Periodic Matrices</a> %Y A111485 Cf. A072148. %K A111485 hard,nonn %O A111485 1,2 %A A111485 _Wouter Meeussen_, Nov 15 2005