def styblinski_tang(ind):
    """Styblinski-Tang function defined as:
    $$ f(x) = 1/2 \sum_{i=1}^{n} x_i^4 - 16 x_i^2 + 5 x_i $$
    with a search domain of $-5 < x_i < 5, 1 \leq i \leq n$.
    """
    return sum(((x ** 4.) - 16. * (x ** 2.) + 5. * x for x in ind)) / 2.,