I agree, downvoting would be a useful mechanism to flag poorly written katas and/or encourage authors to fix them. Any user with a given account age/level of community engagement/# of katas solved/whatever should be able to downvote. Right now total upvotes is not useful info--it's just a proxy for length of time a kata has been on the site, since there's no way to reverse the trend.

If it times out it means your loop isn't exiting for some reason.

Anyway, thank for the feedback!

It's up to the codewarrior to discover that with some given n it's impossible to remove two numbers verifying the conditions, hence my friend was cheating.

Good point but

In a sequence of numbers from 1 to n (n > 0 given) a friend of mine has removed two numbers but it tells me that the product of the two removed numbers is equal to the sum of the numbers he left in the sequence.

Above is the truth, hence you can find when it's not the truth:-)