请编写一个Python程序，输出斐波那契数列的前20项。
def fibonacci(): 
    # TODO: Generate the Fibonacci sequence 
    return fib_seq
print(fibonacci())
```
def fibonacci(): 
    fib_seq = [0, 1]
    for i in range(2, 20):
        fib_seq.append(fib_seq[i-1]+fib_seq[i-2])
    return fib_seq

print(fibonacci())
```

输出结果：

```
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181]
```