Solution: Each year’s temperature anomaly has $7$ possible integer values: $-3, -2, -1, 0, 1, 2, 3$. For the first year, there are $7$ choices since no restriction applies. For each subsequent year, the anomaly must differ from the previous year’s, so there are $6$ choices. Since there are $7$ years and only the first choice is unrestricted, the total number of valid sequences is: - Portal da Acústica