Given letters = ['A','B','C'] and numbers = list(range(10)), build a MultiIndex whose entries are every combination of one letter and one number (30 combinations total, ordered with letters varying slowest) and use it to index a Series. For reproducibility use values 0, 1, …, 29. Return the Series.

Output

A  0     0
   1     1
   2     2
   3     3
   4     4
        ..
C  5    25
   6    26
   7    27
   8    28
   9    29
Length: 30, dtype: int64