Integers with Prime Values of Divisor Sum/Mistake

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): $16$