def sequential_from_scheme(scheme, num_bins):
    """
    Each sequential scheme in Colorbrewer has 13 values, and a subset of these is returned depending on the number of bins selected by the user. 
    This is a utility function which returns the colors in a specific brew given the entire scheme. 
    For details see: http://www.albany.edu/faculty/fboscoe/papers/harrower2003.pdf, table 1
    """
    sequencedict={
        3: (3, 6, 9),
        4: (2, 5, 7, 10),
        5: (2, 5, 7, 9, 11),
        6: (2, 4, 6, 7, 9, 11),
        7: (2, 4, 6, 7, 8, 10, 12),
        8: (1, 3, 4, 6, 7, 8, 10, 12),
        9: (1, 3, 4, 6, 7, 8, 10, 11, 13)  
    }
    return tuple([scheme[x-1] for x in sequencedict[num_bins]])