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Number Chain

Problem

A chain of numbers is made by using the following rule:

Divide by 5 if the number is divisible by 5 otherwise add 4.

For example, starting with the number 7,


It can be seen that the chain has returned to 7.

Which positive integer below 10 will never come back to itself?

Problem ID: 80 (Oct 2002)     Difficulty: 1 Star

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