What is the minimal number of moves in backgammon such that the initial board configuration is exactly...

competition/games/backgammon New

New entry, edited from material collected for the archive and not yet in a released version.

Problem

What is the minimal number of moves in backgammon such that the
initial board configuration is exactly replicated
  a) for one of the players
  b) for both players?

Show solution

Here's a sequence which gets both players back to the starting blocks
in what is probably the minimum number of moves:

        X Roll        Move                O Roll        Move

        21      6/3                21        1/3*, 19/20
        56        B/20*/14        16        B/1, 3/9
        62        14/6                64        9/19

-- Justin Boyan <jab@CS.CMU.EDU>

[ Editor: the puzzle was posed by Dragomir R. Radev
<radev@news.cs.columbia.edu>; no answer to part (a) was given. ]