Integers with Prime Values of Divisor Sum/Mistake
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Source Work
1997: David Wells: Curious and Interesting Numbers (2nd ed.):
- The Dictionary
- $16$
Mistake
- $\map \sigma {16} = 31$ is prime. The sequence of $n$ for which $\map \sigma n$ is prime runs: $2, 4, 9, 16, 25, 289 \ldots$
This is incorrect.
The correct sequence is:
- $2, 4, 9, 16, 25, 64, 289 \ldots$
This sequence is A023194 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008).
Sources
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $16$