Cards around a circle
Source: Kürschak 2007, problem 1
July 8, 2014
parameterizationcombinatorics unsolvedcombinatorics
Problem Statement
We have placed cards around a circle, facing downwards. In one step we may perform the following operation with three consecutive cards. Calling the one on the center , the two on the ends and , we put card in the place of , then move and to the places originally occupied by and , respectively. Meanwhile, we flip the cards and .Using a number of these steps, is it possible to move each card to its original place, but facing upwards?