How many of the numbers from the set \(\{1,\ 2,\ 3,\ldots,\ 50\}\) have a perfect square factor other than one?

I think you mean

4 9 16 25 36 49 Six

I count 18 which have at least 1 perfect square as a factor or divisor:

(4, 8, 9, 12, 16, 18, 20, 24, 25, 27, 28, 32, 36, 40, 44, 45, 48, 50)

Don't forget 49

Right. Thanks.