Write a function to find eulerian number a(n, m).
def eulerian_num(n, m): 
	if (m >= n or n == 0): 
		return 0 
	if (m == 0): 
		return 1 
	return ((n - m) * eulerian_num(n - 1, m - 1) +(m + 1) * eulerian_num(n - 1, m))
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to find eulerian number a(n, m).
def eulerian_num(n, m): 
	if (m >= n or n == 0): 
		return 0 
	if (m == 0): 
		return 1 
	return ((n - m) * eulerian_num(n - 1, m - 1) +(m + 1) * eulerian_num(n - 1, m))[/INST]assert eulerian_num(3, 1) == 4
assert eulerian_num(4, 1) == 11
assert eulerian_num(5, 3) == 26</s>