Generate the Sequence

Let’s play a game.

1 2 3 3 4 5 5 4 5 7 8 7 7 8 7 5 6 9 11 10 11 13 12 9 9 12 13 11 10 11 9 6 7 11 14 …

You have 5 minutes to describe a method to generate this sequence.

Another number! Blood please.

Choose random numbers between 1 and 15.

Ok, ok, here’s a real one :
Write : {1 2 3 3 4 5 5 4 5 7 8 7 7 8 7 5 6 9 11 10 11 13 12 9 9 12 13 11 10 11 9 6 7 11 14}
Repeat

What?

Ok I did. I was asked to write it and not type it so there.