by Nick MacKinnon
Published Sunday April 12 2020 (link)
My aunt has a collection of sovereigns, and she set me a challenge. “You can have the coins if you can work out the dates, which (in increasing order) are equally spaced and all in the 20th century. The number of coins is an odd prime. The highest common factor of each pair of dates is an odd prime. The sum of the number of factors of each of the dates (including 1 and the date itself) is an odd prime.” I worked out the dates, though the gift was much less valuable than I’d hoped.
What were the dates?