I hit "Send" too soon; there is a slight error in the directions for
"extra credit".

The corrected version is below:

For extra credit, try the following.

Start with your list of 400 numbers, and on some other line type an
asterisk. Select the list of numbers and convert it to a two-column
table. Select and copy the asterisk, select the cells in all but the
first row of the last column in the table, and paste the asterisk.
Convert the table back to text, separating on paragraph marks not tab
characters.

Now look down the list for the next (ignore the 1) non-asterisk number
(3), select the list and convert it to a table with that many columns.
Select the cells in all but the first row of the last column in the
table, and paste the asterisk. Convert the table back to text,
separating on paragraph marks not tab characters.

Do this whole process again for the next non-asterisk number (5), and
keep doing it until the smallest number that is not 1 or an asterisk
is greater than 20.

At this point you have a list of all the prime numbers less than 400,
without typing a single number or doing any arithmetic.

Wish me luck, I am about to hit "Send" again...

Bob S