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Number Theory Level 4

Let $$d(n)$$ be the number of positive factors, including $$1$$ and $$n$$, of a positive integer $$n$$. Find the sum of all $$n$$ such that $$d(n) = \dfrac{n}{3}$$.

Any elegant proofs of why these are the only such values of $$n$$ are welcome but not required.

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