Answer:
Unidentifiable.
Step-by-step explanation:
8 to 13 is +5. 13 to 6 is -7. 6 to -16 is -20. -20 to -49 is -19. -49 to -82 is -33.
There is no distinguishable pattern since the differences between the terms vary significantly and in unpredictable ways. Make sure to double check you've got all your numbers correctly. <3