A group of students is arranging squares into layers to create a project. The first layer has 4 squares. The second layer has 8 squares. Which formula represents an arithmetic explicit formula to determine the number of squares in each layer? f(1) = 4; f(n) = 4 ⋅ d(n − 1), n > 0
f(1) = 4; f(n) = 4 ⋅ d(n + 1), n > 0
f(1) = 4; f(n) = 4 + d(n + 1), n > 0
f(1) = 4; f(n) = 4 + d(n − 1), n > 0