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To be fair, the article also says:

> That is, these numbers are not in the image of the aliquot sum [0] function.

And that function is specifically defined, using ∑ notation, as the sum of all (distinct) integers that are the proper divisors of its input.

More generally, in my experience, uniqueness is generally assumed when talking about divisor sums and their variants, unless otherwise indicated.

[0] https://en.wikipedia.org/wiki/Aliquot_sum




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