# Series Formulas

## Arithmetic series

An arithmetic series is a sequence of numbers in which the difference between any two consecutive terms is constant. This constant difference is known as the “common difference.” The sum of the terms in an arithmetic series can be calculated using a formula.

S = n / 2 ( 2a + (n - 1)d)

## Geometric series

A geometric series, on the other hand, is a sequence of numbers in which each term after the first is obtained by multiplying the previous term by a fixed, non-zero number called the “common ratio.” The sum of the terms in a geometric series can also be calculated using a formula.

S = a ( 1 - r^n) / ( 1 - r)

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