It seems you've uploaded an image containing the summation symbol, $\Sigma$. The summation notation, represented by the Greek letter Sigma ($\Sigma$), is commonly used in mathematics to indicate the sum of a sequence of numbers or expressions.

If you have a specific summation problem or an equation involving summation that you'd like help with, please provide further details or a related question.

Would you like to see examples, or do you have specific values, limits, or expressions for this summation?

Here are five related questions that might help deepen understanding:

1. What is the basic formula for calculating the sum of a series?
2. How does summation work for an arithmetic sequence?
3. How does summation work for a geometric sequence?
4. What are the upper and lower bounds in summation notation?
5. How can summation notation be applied in calculus?

Tip: In summation notation, the expression below the $\Sigma$ symbol often indicates the starting value of the index, while the expression above indicates the ending value.