1/2 − 1/4 + 1/8 − 1/16 + ⋯
In mathematics, the infinite series 1/2 − 1/4 + 1/8 − 1/16 + ⋯
is a simple example of an alternating series that converges absolutely.
It is a geometric series whose first term is 1/2 and whose common ratio is −1/2, so its sum is Wikipedia