历届部分选解

找了比较难的来解。数列一定要做！！！

https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B545VXSP9sY8YTRjODdiZTctOWRlZS00MjIwLWFiZTYtZTFmNGUzYzU4YWRk&hl=en_US