Reply to comment

10 lucky Daltons

Each cell number 1-100 (say it k) is the product of two integers, say m*n. If k is prime, there is only one pair of (m, n); otherwise there are more.

Doors, being initially locked ("There are 100 prisoners in 100 separate locked cells."), prison officer m (m is a divisor of k) visits the cell k and unlocks it, while later prison officer n in its visit locks the cell.

Lucky cells are 10: those that have odd number of divisors, where m=n, that means no prison officer visits the cell later, which means k = perfect square
1, 4, 9, 16, 25, 36, 49, 64, 81, 100.


  • Web page addresses and e-mail addresses turn into links automatically.
  • Allowed HTML tags: <a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd>
  • Lines and paragraphs break automatically.

More information about formatting options

To prevent automated spam submissions leave this field empty.
By submitting this form, you accept the Mollom privacy policy.