Quandaries
and Queries |
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Who is asking: Student Level: Secondary Question: |
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Hi Arne, This is a nice observation. It is in fact true, the units digit of a divisor of n² + n - 1 can not be 3 or 7. The proof I have shows that the result is true for prime factors and then uses properties of a particular quadratic form to exend he result to all factors. Thanks for the question, Richard |