Given an arithmetic progression (an) find a13 if a1 = 2 and d = 4

As you know, an arithmetic progression is a sequence (with finite or infinite terms) of numbers an, which has the following property: an + 1 = an + d, where n = 1, 2,…. The number d is called a step (there is another name: difference). If the first term a1 and the step d of an arithmetic progression are given, then such an arithmetic progression is considered completely given.
The task gives the first term a1 = 2 and step d = 4 of the arithmetic progression an. It is required to calculate the value of the thirteenth term a13 of this arithmetic progression. Let’s use the formula: an = a1 + d * (n – 1), where n = 1, 2,…. We have: a13 = a1 + d * (13 – 1) = 2 + 4 * (13 – 1) = 2 + 4 * 12 = 2 + 48 = 50.
Answer: a13 = 50.