A sequence is an arrangement of numbers in a definite order according to some rule.
The various numbers occurring in a sequence are called its terms. We denote the terms of a sequence by a1, a2, a3…etc. Here, the subscripts denote the positions of the terms. In general, the number at the nth place is called the nth term of the sequence and is denoted by an. The nth term is also called the general term of the sequence.
A sequence is said to be in geometric progression or G.P. if the ratio of any term to its preceding term is the same throughout. Constant Ratio is a common ratio denoted by ‘r’.