All the squares less than 50 are

0²=0, 1²=1, 2²=4, 3²=9, 4²=16, 5²=25, 6²=36, 7²=49.

They are 1, 4, 9, 16, 25, 36, 49

The only odd ones are 1, 9, 25, and 49. That's the answer.

If we had known that the squares of even numbers are always even, and
squares of odd numbers are always odd, we would have known just to list.

1², 3², 5², and 7² and we wouldn't have needed to list the even ones.

Edwin