2,15,3,11,6,7,9,3,12

The sequence provided is 2, 15, 3, 11, 6, 7, 9, 3, 12. To identify the pattern, we can split it into two interleaved subsequences:

1. Odd-indexed terms (positions 1, 3, 5, 7, 9):

2, 3, 6, 9, 12

2. Even-indexed terms (positions 2, 4, 6, 8):

15, 11, 7, 3

Full sequence continuation:

After 12 (position 9), the next term (position 10) belongs to the even-indexed subsequence.

Next number in the sequence:

`-1`

Extended sequence:

2, 15, 3, 11, 6, 7, 9, 3, 12, -1, 15, -5, 18, -9, ...