Sequence Guess

Guess the sequence. The solutions is near.

Sequence: 1 2 1 -1 -2 -1 1 2 1 -1 -2 -1 1

The solution is:

1 2

And the recurrence formula is

seq[-1] -seq[-2]

This fine program was brought to you by hakank@bonetmail.com
My other useless programs.