A111485 - OEIS

%I #7 Feb 16 2025 08:32:58

%S 1,3,12,107,951,10923

%N Number of (-1,0,1) periodic irreducible matrices up to sign change, transposition and mirroring over the antidiagonal.

%C "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 Wouter Meeussen, <a href="http://users.pandora.be/Wouter.Meeussen/PseudoAntiSymmetricMatrixPowers.nb">Periodic</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PeriodicMatrix.html">Periodic Matrices</a>

%Y Cf. A072148.

%K hard,nonn,changed

%O 1,2

%A _Wouter Meeussen_, Nov 15 2005