Square Numbers which are Divisor Sum values/Mistake

Source Work

 * The Dictionary
 * $36$
 * $36$

Mistake

 * ''The sequence of squares which are values of $\map \sigma n$ goes: $1 \ \ 4 \ \ 36 \ \ 121 \ \ 144 \ \ 256 \ \ 576 \ \ldots$

Correction
$400$ is missing from this list.