1 − 2 + 3 − 4 + ⋯

In mathematics, $1 − 2 + 3 − 4 + ···$ is an 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

$\displaystyle \sum _{n=1}^{m}n(-1)^{n-1}.$

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