Just to be sure I understand: 1. Are you referring to n x n matrices M = (m_ij) with all entries in {-1,0,1} such that i <> j => m_ij + m_ji = 0 ? 2. Do your divisors of 12 (for n = 6) include 12 itself? 3. What exactly is meant by "block matrices along the diagonal" ? Thanks for clarification, Dan -------------------------------------------------------------------------------------- Wouter wrote: << of the pseudo-anti-symmetric type (sum of anti-symmetric and diagonal). A072148. (cfr Aug 2003). Just submitted result for n=6. The periods still are divisors of 12. Weird. Realised that block matrices along the diagonal are cheap and predictable. So I did a count without'm, and eliminated sign change, transposes and mirroring over the anti-diagonal too. Got 1, 3, 12, 107, 951, 10923... (under submission). Funny property: only the even n give some matrices with all-zero diagonals, the odd n don't. But why period k | 12 ?

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