from typing import Sequence
from typing import List


def order_rep(
    pcset: Sequence
) -> List:

    """ Given a tone row, returns a list of pairs [i,ai],
    on which i is the order number and ai is the pitch class
    at that order number. Inspired by Milton Babbitt.
    """

    return [tuple([i,el]) for i, el in enumerate(pcset)]