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# Equal ratio series calculator _ online calculation tool

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an Sn

Geometric sequence equal ratio sequence

A geometric sequence means that if a sequence is from item 2, the ratio of each item to its previous item is equal to the same constant. This constant is called the ratio of the geometric series，the common ratio is usually represented by the letter q as (q≠0), and the ratio $$a1≠ 0$$. Note: When q=1, an is a constant column.

Equal ratio series formula

1.General formula：$$an=a1q^{n-1}$$

2.Summation formula:

$$Sn=na1$$(q=1)

$$Sn= \frac {a1(1-q^n)}{1-q}$$(q≠1）