Stage: 3 Challenge Level: 
How many tricolour flags are possible with 5 available colours
such that two adjacent stripes must NOT be the same colour. What
about 256 colours? 
<-- Here's an example for 3 colours.
Combinations. Mathematical reasoning & proof. Combinatorics. Selecting and using information. Counting. Permutations. Interactivities. Networks/Graph Theory. Working systematically. Visualising.
Published May 1999.
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