diff --git a/html-src/rules/hanoipuzzle.html b/html-src/rules/hanoipuzzle.html
index e194878d4..8f43ed270 100644
--- a/html-src/rules/hanoipuzzle.html
+++ b/html-src/rules/hanoipuzzle.html
@@ -26,4 +26,5 @@ <h3>History</h3>
 puzzle.  It is traditionally played with different size disks.
 <p>
 For a given number of cards, the minimum number of moves to solve
-the puzzle is one less than double the number of cards (2n - 1).
+the puzzle is one less than two to a power of the number of cards
+(2^n - 1).