def this_leibniz_term(term_index):
    """
    Calculates a single term in the version of the Gregory-Leibniz series for calculating Pi from Pi/4.
    Note that this particular method is conceptually very simple, but converges very slowly.
    See README.md for more discussion.
    
    """
    return (4.0/(term_index*2+1))*((-1)**(term_index))