# Math Help - Express in sigma notation

1. ## Express in sigma notation

nb

2. Originally Posted by oceanmd
$1/e+2/e^2+3/e^3+4/e^4+....+an$ (n lower than a)

I am not sure how to do it.
Is it sigma sign, on top n, on the botton k+1, next to it k/e^k

is this what you are describing? $\sum_{k = 1}^{n} \frac k{e^k}$