Number of iterations in bubblesort with diagram

def bubblesortIterations(arrayLength):
    iterations = 0
    for i in range(arrayLength-1):
        for j in range(i+1, arrayLength):
            iterations += 1
    return iterations

# MAIN FUNCTION
print()
print("When n = 4 in an array = [0, 1, 2, 3] I have 6 checks: (01), (02), (03), (12), (13), (23)")
print("So there are c(n,2) = c(4,2) = 6 checks here.")
print("c(n,2) = n! / (2! * (n-2)!) = n*(n-1)/2 = O(n^2)")
print("It will be proved with the diagram below.")
print()

from matplotlib import pyplot as plt
N = 20
nList = list(range(1, N + 1))
iterationsList = list()
for n in nList:
    iterations = bubblesortIterations(n)
    iterationsList.append(iterations)
    print("n = " + str(n) + " ----> " + str(iterations) + " iterations")

plt.plot(nList, iterationsList, 'o', label="Iterations when using bubblesort")
plt.xlabel("n = num of elements")
plt.ylabel("Iterations = O(n^2)")
plt.legend()
plt.show()