Sequence of Record Peaks in Values of Divisor Sum
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Theorem
Let $d: \Z_{>0} \to \Z_{>0}$ be the mapping defined as:
- $\map d n = \map {\sigma_1} n - \map {\sigma_1} {n'}$
where:
- $n$ denotes a highly abundant number
- $n'$ denotes the previous highly abundant number.
The following $n \in \Z_{>0}$ have the property that they have a higher value of $\map d n$ than any smaller $n$:
- $\forall m \in \Z_{>0}: m < n \implies \map {\sigma_1} m < \map {\sigma_1} n$
That is, they are the peak divisor sums which exceed the previous peak by a higher number than any previous peak.
That is, they are highly abundant number which have divisor sums whose difference with that of the divisor sum of the previous highly abundant numbers is greater than that with the previous record difference.
$n$ $n'$ $\map {\sigma_1} n$ $\map {\sigma_1} {n'}$ $\map d n$ $2$ $1$ $3$ $1$ $2$ $4$ $3$ $7$ $4$ $3$ $6$ $4$ $12$ $7$ $5$ $12$ $10$ $28$ $18$ $10$ $24$ $20$ $60$ $42$ $18$ $36$ $30$ $91$ $72$ $19$ $48$ $42$ $124$ $96$ $28$ $60$ $48$ $168$ $124$ $44$ $120$ $108$ $360$ $280$ $80$
Sources
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $168$