# Arithmetic and geometric sequence.

An article sequence is a recursive sequence that has the same difference, the common difference, between any pair of consecutive terms. An arithmetic sequence can be defined as the following:

an=a+(n-1)d

d=common difference.

a=first term of the sequence.

an=nth term of the sequence.

A geometric sequence is defined as a sequence that has the same ratio, the common ratio, between any pair of consecutive terms. The geometric sequence can be represented as the following formula:

an=ar^(n-1)

an=nth term of the sequence.

a=first term of the sequence.

r=common ratio.