Chapter 10 - Section 10.1 - Sequences and Summation Notation - Exercise Set - Page 1048: 45

$\sum_{i=1}^{11} 2^i$

In order to set up the summation notation, we must calculate the value which keeps constantly changing. That value will be designated as the $i$ term . The remaining terms that are the same would remain the same or constant in the summation notation. Thus, we get the summation notation such as: $\sum_{i=1}^{11} 2^i$