2017-11-08 17:39:50 +01:00
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A number chain is created by continuously adding the square of the digits in a number to
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form a new number until it has been seen before.
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For example,
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2019-05-27 23:10:30 +02:00
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~~~
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44 -> 32 -> 13 -> 10 -> 1 -> 1
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85 -> 89 -> 145 -> 42 -> 20 -> 4 -> 16 -> 37 -> 58 -> 89
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~~~
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2017-11-08 17:39:50 +01:00
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Therefore any chain that arrives at 1 or 89 will become stuck in an endless loop.
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What is most amazing is that EVERY starting number will eventually arrive at 1 or 89.
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How many starting numbers below ten million will arrive at 89?
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