def cohort_to_int(year, season, base=16):
    """cohort_to_int(year, season[, base])

    Converts cohort tuple to a unique sequential ID.

    Positional arguments:
        year (int) - 2-digit year
        season (int) - season ID

    Keyword arguments:
        base (int) - base year to treat as 0

    Returns:
        (int) - integer representing the number of seasons since the beginning
            of the base year
    """

    return 3*(year - base) + season