[Retros] Challenge

[Noam Elkies]

Andrew Buchanan <andrew at anselan.com> writes:


> Sorry to go on about it Juha, but as far as the infinite case

> is concerned, I think the minimum position has 5 units, e.g.:



> 8/8/8/8/8/8/7p/3BK1bk

> #n exactly, for all n


This may be minimal in material, but for piece count one can do better:
Kf6,Qh3(or h7) / Kf8,Qd7.


> The key is well defined for each #n, but later play is not unique,

> short mates exist, and keys are not unique over all n.


Likewise here.  It is clear a priori that the keys cannot be unique
over all n because on a finite chessboard there are only finitely many
moves from the diagram.

NDE