Triplet in Arithmetic Sequence with equal Divisor Sum
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Theorem
The smallest triple of integers in arithmetic sequence which have the same divisor sum is:
- $\map {\sigma_1} {267} = \map {\sigma_1} {295} = \map {\sigma_1} {323} = 360$
Proof
We have that:
\(\ds 295 - 267\) | \(=\) | \(\ds 28\) | ||||||||||||
\(\ds 323 - 295\) | \(=\) | \(\ds 28\) |
demonstrating that $267, 295, 323$ are in arithmetic sequence with common difference $28$.
Then:
\(\ds \map {\sigma_1} {267}\) | \(=\) | \(\ds 360\) | $\sigma_1$ of $267$ | |||||||||||
\(\ds \map {\sigma_1} {295}\) | \(=\) | \(\ds 360\) | $\sigma_1$ of $295$ | |||||||||||
\(\ds \map {\sigma_1} {323}\) | \(=\) | \(\ds 360\) | $\sigma_1$ of $323$ |
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Sources
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $267$