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Find the greatest prime divisor of the value of the arithmetic series
1 + 2 + 3 + \dots + 135 + 136 + 137 + 138 + 139 + 140.

 Jun 16, 2024
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Using the arithmetic series formula, we find the sum is \(\frac{(140+1)(70)}{2}\), which is 141*35. Now that we have a factorization, we can easily find the greatest prime divisor. The prime factorization is 3*5*7*47, so the greatest prime divisor is \(47\).

 

Feel free to tell me if I did anything wrong! :D

 Jun 19, 2024

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