如何去写这个程序，不知道该怎么先去定义函数
def combination(n,i):
sum=1
sum2=1
for j in range(1,i+1):
sum=sum*n
n=n-1
sum2*=j
print(sum//sum2,end=' ')
n=4
for i in range(0,n+1):
combination(n,i)
def combination(n,i):
sum=1
sum2=1
for j in range(1,i+1):
sum=sum*n
n=n-1
sum2*=j
print(sum//sum2,end=' ')
n=4
for i in range(0,n+1):
combination(n,i)