def pochhammer(x, k):
    """Compute the pochhammer symbol (x)_k.

    (x)_k = x * (x+1) * (x+2) *...* (x+k-1)

    Args:
        x: positive int
    Returns:
        float for (x)_k
    """
    xf = float(x)
    for n in range(x+1, x+k):
        xf *= n
    return xf