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positive multiple of a semiperfect number is also semiperfect
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(Derivation)
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Just as the theorem on multiples of abundant numbers shows that multiples of abundant numbers are also abundant, it is also true that multiples of semiperfect numbers are also semiperfect, and T. Foregger's proof of the abundant number theorem lays bare a simple mechanism that we can also employ for semiperfect
numbers.
Given the divisors $d_1, \ldots, d_{k - 1}$ of $n$ (where $k = \tau(n)$ and $\tau(x)$ is the divisor function), sorted in ascending order for our convenience, and with a smart iterator $i$ that somehow knows to skip over those divisors that contribute to $n$ 's abundance, we can show that the divisors of $nm$ (with
$m > 0$ ) will include $d_1m, \ldots, d_{k - 1}m$ . With our smart iterator $i$ and thanks to the distributive property of multiplication, it follows that $$\sum_{i = 1}^{k - 1} d_im = nm,$$ our desired result.
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"positive multiple of a semiperfect number is also semiperfect" is owned by PrimeFan. [ owner history (1) ]
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Cross-references: multiplication, distributive property, abundance, iterator, ascending order, divisor function, divisors, simple, theorem, proof, semiperfect numbers, abundant numbers, multiples, theorem on multiples of abundant numbers
This is version 1 of positive multiple of a semiperfect number is also semiperfect, born on 2006-10-10.
Object id is 8441, canonical name is PositiveMultipleOfASemiperfectNumberIsAlsoSemiperfect.
Accessed 813 times total.
Classification:
| AMS MSC: | 11A05 (Number theory :: Elementary number theory :: Multiplicative structure; Euclidean algorithm; greatest common divisors) |
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Pending Errata and Addenda
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