[Math] What's next?

Hey guys. I'm back yet again with a different type of math game.

Here's the basics:

I will give you guys a series of numbers. You have to tell me what number/numbers is/are next... and why. Most creative person wins it. You can outdo someone's creativity even if we passed that question a LONG while back. "most creative" is entirely up to me and as such is not up for debate

Example series:

1) 1, 2, 3

Example responses:

1) 1, 2, 3

4, 5, 6; because you just add 1 each time.

1) 1, 2, 3

4, 6; it's numbers that divide into the number 6

The second response wins it. They both quoted the original problem to denote the sequence they're responding to.

A few days later even though we're on a new question....

1) 1, 2, 3

2, 1, 2, 3; it oscillates from 1 to 3

This new poster wins it and takes place of most creative.

Notes:
I'll update the second post with all of the questions and best answers.
The series do not necessarily have to go on forever (but can).
It could just end at the numbers you gave... or keep going from there, that won't make a difference in judging.


You each get ONE shot at responding to each series. No edits please :3