## Initial term of arithmetic progression or arithmetic sequence (given n-th term,arithmetic series)

### Formula

a1
initial term
Sn
arithmetic series, sum of n elements
an
n-th term
n
number of elements

### Formula description

In mathematics, an arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. For instance, the sequence 3, 5, 7, 9, 11, 13, ... is an arithmetic progression with common difference 2. The sum of the members of a finite arithmetic progression is called an arithmetic series.

Sn
an
n
a1
Precision

### References

1. wikipedia: Arithmetic progression.

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