Question: 
Write a python function to find nth bell number.


Model's Code:
def bell_Number(n):
    bell = [[0 for _ in range(n+1)] for _ in range(n+1)]
    bell[0][0] = 1

    for i in range(1, n+1):
        bell[i][0] = bell[i-1][i-1]

        for j in range(1, i+1):
            bell[i][j] = bell[i-1][j-1] + bell[i][j-1]

    return bell[n][0]



Sample Correct Code:
def bell_Number(n): 
    bell = [[0 for i in range(n+1)] for j in range(n+1)] 
    bell[0][0] = 1
    for i in range(1, n+1):
        bell[i][0] = bell[i-1][i-1]
        for j in range(1, i+1): 
            bell[i][j] = bell[i-1][j-1] + bell[i][j-1] 
    return bell[n][0] 


Asserts:
assert bell_Number(2) == 2
assert bell_Number(3) == 5
assert bell_Number(4) == 15


Tests:
Test 1 of 3: PASS
Test 2 of 3: PASS
Test 3 of 3: PASS

Test 608 of 974: 453/608 (74.50657894736842%): success