import numpy as np

A= np.array([[ 0,  1,  2],
              [ 1,  1,  6],
              [ 2,  2, 10],
              [ 3,  2, 14]])
# Find the split indices
i = np.nonzero(np.diff(A[:, 1]))[0] + 1
i = np.insert(i, 0, 0)
# Compute the result columns
c0 = np.arange(i.size)
c1 = A[i, 1]
c2 = np.add.reduceat(A[:, 2], i)
# Concatenate the columns
result = np.c_[c0, c1, c2]

print(result)