2010 China Second Round,test 2,problem 4
Source:
February 11, 2012
linear algebramatrixcombinatorics proposedcombinatorics
Problem Statement
the code system of a new 'MO lock' is a regular -gon,each vertex labelled a number or and coloured red or blue.it is known that for any two adjacent vertices,either their numbers or colours coincide.
find the number of all possible codes(in terms of ).