How it is calculated
In a geometric progression the step field is the ratio each following term is multiplied by. If that ratio is 1, the sum equals the first term multiplied by n.
a_n = a + (n − 1) d, S = n / 2 × (2a + (n − 1) d)
Where the numbers come from
- Kind
- First term
- Step or common ratio
- Term number
Example
An arithmetic progression: first term 2, common difference 3, index 5. The term is 14, and the sum of five terms is 40.
Questions
Does numbering start at 1?
Yes. The first term is number 1, and it equals the start you entered.
A negative denominator?
Yes. The terms will alternate in sign.
The sum of an infinite series?
No, only the first n terms, a finite sum.