 However, if we want the same precision for we must evaluate and sum the first five terms of the series.For , one requires the first 18 terms of the series, and for we need to evaluate the first 141 terms.So for these particular values the fastest convergence of a power series expansion is at the center, and as one moves away from the center of convergence, the rate of convergence slows down until you reach the boundary (if it exists) and cross over, in which case the series will diverge.