Arithmetic progression

In mathematics, an arithmetic progression, or arithmetic sequence, is a sequence with the property that the difference between the two terms which follow one another is constant. This is different from a geometric progression, where the ratio of change between two terms is constant.
If the initial term of an arithmetic progression is ${\displaystyle a_{1}$ and the common difference of successive members is ${\displaystyle d}$, then the ${\displaystyle n}$-th term of the sequence (${\displaystyle a_{n}$) is given by:

${\displaystyle a_{n}=a_{1}+(n-1)d}$

A finite portion of an arithmetic progression is called a finite arithmetic progression and sometimes just called an arithmetic progression. The sum of a finite arithmetic progression is called an arithmetic series.

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