Summation is the addition of a sequence of numbers, expressed with sigma notation in the general form:

where . We read this as adding up the terms as ranges over the integers from as its lower index to as its upper index. Think of it as a for loop!

Closed formulas

We additionally have some closed formulas:

Properties

For a constant , as a consequence of the distributive property of real numbers:

Due to the commutative property of real numbers, when we have addition or subtraction of terms: