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by zmgsabst
171 days ago
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3 is also the product of the sets {3, 1}, {3, 1, 1}, etc. We’re excluding the unit when defining these factor sets (ie, multiplicative identity) because it removes unique factorization. That 1 is the unit is also why it’s the value for the product of the empty set because we want the product of a union of sets to match the product of a product of sets. But we don’t exclude it from the primes for that reason. |
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