1, 52,3 1 3, 174, the first number is 1, 5,3, 1, then the next first number is 5, and the last number is1,2, 2. Is the tenth digit of the third number (3 13), and the sum of the single digits of the second number and the tenth digit is 2+5=7, which is the tenth digit of the fourth number (174), so the tenth digit of the fifth number is equal to the single digits of the third number and X=3+ 1=4, so

If there is such a doubt, it is a bit abnormal.

1,2,3,7, 16,65,()

Solution: the square of 1 +2 = 3.

2 squared +2 = 7

3 squared +7 = 16

16+65 squared = 32 1