divergent
1311 − 2 + 3 − 4 + · · · — In mathematics, 1 − 2 + 3 − 4 + … is the infinite series whose terms are the successive positive integers, given alternating signs. Using sigma summation notation the sum of the first m terms of the series can be expressed as:sum {n=1}^m n( 1)^{n …
132Corrective lens — A bifocal corrective eyeglass lens A pair of contact le …
