class Solution:
def numberOfArithmeticSlices(self, sequence):
n = len(sequence)
count = 0
prev_count = defaultdict(int)
for i in range(n):
candidates = Counter(sequence[i + 1])
for j in range(i + 1, n):
candidates[sequence[j]] -= 1
count += candidates[sequence[j] + (sequence[j] - sequence[i])]
return count