Question: 
Write a function to find the nth nonagonal number.


Model's Code:
def is_nonagonal(n):
    return n * (7 * n - 5) // 2



Sample Correct Code:
def is_nonagonal(n): 
	return int(n * (7 * n - 5) / 2) 


Asserts:
assert is_nonagonal(10) == 325
assert is_nonagonal(15) == 750
assert is_nonagonal(18) == 1089


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

Test 641 of 974: 478/641 (74.57098283931357%): success