If you mean, what is the pattern, it is the first three prime numbers. The next one would be 7, then 11, then 13 and so on.
Also, there is a sequence of numbers called the Fibonacci sequence, which goes 1, 1, 2, 3, 5, 8, 13, 21, ... (you add the two previous numbers to get the next one). Although your numbers 2, 3, 5 are in this list, I don't think that is what is meant by your example, since the 1, 1 are missing in the beginning.
So, I would say, "it is the first three prime numbers".