When is 1+2+ +n a perfect square?

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SUMMARY

The discussion focuses on identifying values of n (where n ≥ 1) for which the sum of factorials, specifically 1! + 2! + ... + n!, results in a perfect square. It is established that n=1 and n=3 yield perfect squares, while the participant expresses uncertainty about finding additional values or proving the absence of others. The mention of quadratic residues serves as a hint for further exploration in this mathematical problem.

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Homework Statement


Find the values of [tex]n\geq 1[/tex] for which 1! + 2! + ... + n! is a perfect square in the integers.


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The Attempt at a Solution


n=1 and n=3 works, but I don't know how to find anymore, or prove that there aren't anymore
 
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Do you know about quadratic residues? If so, that's a hint.
 
Petek said:
Do you know about quadratic residues? If so, that's a hint.

well I proved it, thanks
 

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