3. (20 points) How many numbers from the sequence

20142015, 201402015, 2014002015, 20140002015, 201400002015, ... are perfect squares?
Answer: None.

Solution: The sum of the digits of any number in this sequence is 15. The number 15 is divisible by 3, but not by 9. Therefore, there cannot be any perfect squares in the sequence.