def ref_seq_output(in_seq_name, in_ref_name, ext):
    """
    Generate output file name
    :param in_seq_name: treatment name (str)
    :param in_ref_name: reference name (str)nt)
    :param ext: extension (ie. csv or pdf)
    :return: output filename (str)
    """
    return "{0}_{1}.{2}".format(in_ref_name,
                                in_seq_name,
                                ext)