Is this what you're thinking of? http://en.wikipedia.org/wiki/Impossible_Puzzle Tom rcs@xmission.com writes:
This type of puzzle has been around since at least 1975. Gosper told me the S-and-P puzzle. I hope he can recall the exact details; my memory of it is fuzzed. Roughly (for flavor -- don't waste time trying to solve this): Two players, Sam & Paul. There are two numbers between 1 and 99. Sam is told the sum, Paul is told the product. Each can hear the other's answers; is a perfect logician, etc. Each is asked, in turn, if he knows the numbers. Sam: I don't know. Paul: I don't know. Sam: I don't know. Paul: Now I know. Sam: Now I know too. The puzzle is (of course) "What are the numbers?"
Rich
-------- Quoting Veit Elser <ve10@cornell.edu>:
There is a solution when the inmate is required to flip a coin, so let's stick with that more restrictive variant.
-Veit
On Apr 15, 2015, at 5:47 PM, Cris Moore <moore@santafe.edu> wrote:
Is the inmate allowed to _not_ flip any coin?
Cris