Melody

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Melody  11.02.2022
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Melody  20.12.2021
 #1
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+1

Well the answer is 2 but I do not know how to do it.

 

http://www.wolframalpha.com/input/?i=(sum+from+x%3D1+to+x%3D100+(x%5E3))+mod+7

 

I had done some other work (which i deleted) to decide that the last digit was 0.

I wonder if I can use that fact...

7,14,21,28,35,42,49,56,63,70  It seems multiples of 7 can end in any digit.  That doesn't seem very helpful.

 

I think there is some strange variation on the sum of GP that you can do this with but i have forgotten it...

14.03.2018
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14.03.2018