第二解：

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, … Find the sum of all the even-valued terms in the sequence which do not exceed four million.

解：

```python i = 1 j = 2 sum = 0 while j < 4000000 : if j % 2 == 0 : sum = sum + j t = i i = j j = t + j print sum ```