How do you calculate the following sum?
\begin{equation*} \sum_{i=k}^n i \end{equation*}
How do you calculate the following sum?
\begin{equation*} \sum_{i=k}^n i \end{equation*}
Okay. I was able to find it here, thanks.
http://en.wikipedia.org/wiki/Summation#Some_summations_of_polynomial_expressions
This is a special case for the formula for the sum of n terms in an arithmetic progression:
$\sum_{i=k}^n i = \sum_{i=0}^n i - \sum_{i=0}^{k-1} i = \frac{1}{2} \left[ n(n+1) - (k-1)k \right]$