3. (5 points) There is a class of natural numbers, starting from the third digit from the left, each digit is the sum of the two digits to its left, such as 21347, then among this class of natural numbers, the largest odd number is $\qquad$ .
【Answer】Solution: According to the problem, the highest digit of this natural number can be 1, the second highest digit is 0, and then according to the rule, the digits in the subsequent positions are added successively. Also, since this number is odd, the unit digit should be an odd number, so this number is 1011235. Therefore, the answer is: 1011235.