Copyright © University of Cambridge. All rights reserved.
What is the smallest integer n such that the product $$(2^2 -1)(3^2 -1)(4^2 -1)...(n^2 -1)$$is a perfect square?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.
View the archive of all weekly problems grouped by curriculum topic