Express the following sum in sigma notation: 1+4+7+10+13

The sum would be written as:


It goes from n=1 to =5 because it is the first 5 terms of the sum.
The sequence has a first term, a₁, of 1.  The common difference, d, is 3.  The explicit formula would then be:


Using the distributive property to simplify, we would have: