def get_fourier_col_name(k, col_name, function_name="sin", seas_name=None):
    """Returns column name corresponding to a particular fourier term, as returned by fourier_series_fcn

    :param k: int
        fourier term
    :param col_name: str
        column in the dataframe used to generate fourier series
    :param function_name: str
        sin or cos
    :param seas_name: strcols_interact
        appended to new column names added for fourier terms
    :return: str
        column name in DataFrame returned by fourier_series_fcn
    """
    # patsy doesn't allow "." in formula term. Replace "." with "_" rather than quoting "Q()" all fourier terms
    name = f"{function_name}{k:.0f}_{col_name}"
    if seas_name is not None:
        name = f"{name}_{seas_name}"
    return name