Since you have finite sequences, you can choose any one, and it works. For example, in the first sequence, I can say 24 doesn't belong since every other number listed is the product of at most two primes (but 24 is the product of four primes

).

Alternately, if I consider differences between adjacent terms, I find they are 9-7=2, 13-9=4, 17-13=4, 24-17=7, 35-24=11. Since 35 is the only one that is more than 10 greater than the previous term, I can say that is the one that doesn't belong.

I can create an argument for any term in the sequence. There is no "correct" answer. There are only answer and reason pairs. For each number, I can find a reason why it doesn't belong.

Here are some reasons for the numbers you picked for the next two finite sequences:

1. Neither 250 nor 813 has an element proceeding it.

2.

, so 250 is the only number among the four that is the product of more than three primes (not distinct)

, so 813 is the only number among the four with two prime factors.

3.

, so 250 is the only one that is more than 200 less than the preceding number.

, so 813 is the only one that is more than 200 greater than the preceding number.

The list of reasons why you

**might** choose 250 and 813 respectively is endless.