Question: 
Write a function to find entringer number e(n, k).


Model's Code:
def zigzag(n, k):
    if k == 1:
        return 1
    if k == 2:
        return n
    return (n - 1) * (k - 1) + 1 + (k - 2) // 2 + (k - 2) % 2 * (n - 1)



Sample Correct Code:
def zigzag(n, k): 
	if (n == 0 and k == 0): 
		return 1
	if (k == 0): 
		return 0
	return zigzag(n, k - 1) + zigzag(n - 1, n - k)


Asserts:
assert zigzag(4, 3) == 5
assert zigzag(4, 2) == 4
assert zigzag(3, 1) == 1


Tests:
Test 1 of 3: FAIL: AssertionError()

Test 346 of 974: 250/346 (72.25433526011561%): failed