### Arithmetic Sequences / Progressions

The terms “sequence” and “progression” are interchangeable. An “arithmetic sequence” is the same thing as an “arithmetic progression”. This post uses the term “sequence”… but if you live in a place that tends to use the word “progression” instead, it means exactly the same thing. So, let’s investigate how to create an arithmetic sequence (also known as an arithmetic progression).

Pick a number, any number, and write it down. For example:

Now pick a second number, any number (I’ll choose 3), which we will call the **common difference**. Now **add** the common difference to the first number, then write their sum down to the right of the first number:

Now, continue adding the common difference to the sum and writing the result down… over, and over, and over:

By following this process, you have created an “Arithmetic Sequence”, a sequence of numbers that are all the same distance apart when graphed on a number line:

### Vocabulary and Notation

In the example above 5 is the **first term**, or starting term, of the sequence. To refer to the starting term of a sequence in a generic way that applies to any sequence, mathematicians use the notation

This notation is Continue reading Arithmetic Sequences and Arithmetic Series