'Compute Struve function & error estimate from its power series.'

def _series(self, v, z, n=100):

    k = arange(0, n)
    r = (((((-1) ** k) * ((0.5 * z) ** (((2 * k) + v) + 1))) / special.gamma((k + 1.5))) / special.gamma(((k + v) + 1.5)))
    err = ((abs(r).max() * finfo(float_).eps) * n)
    return (r.sum(), err)
