An arithmetic progression (AP) is a list of numbers in which each term is obtained by adding a fixed number d to the preceding term, except the first term. The fixed number d is called the common difference.

The general form of an AP is a, a + d, a + 2d, a + 3d, . . .

a_n or l or T_n = a + (n - 1)d
Here, a = First Term of an AP
d = Common Difference of an AP
n = No. of terms of an AP
a_n or l or T_n = last term of an AP