对程序做了进一步优化，目前总耗时1分20秒。
代码如下：
运行结果：
满足f(n) = n的n值列表：
1
Total Time: 00:00:00
199981
Total Time: 00:00:00.0156250
199982
Total Time: 00:00:00.0156250
199983
Total Time: 00:00:00.0156250
199984
Total Time: 00:00:00.0156250
199985
Total Time: 00:00:00.0156250
199986
Total Time: 00:00:00.0156250
199987
Total Time: 00:00:00.0156250
199988
Total Time: 00:00:00.0156250
199989
Total Time: 00:00:00.0156250
199990
Total Time: 00:00:00.0156250
200000
Total Time: 00:00:00.0156250
200001
Total Time: 00:00:00.0156250
1599981
Total Time: 00:00:00.0937500
1599982
Total Time: 00:00:00.0937500
1599983
Total Time: 00:00:00.0937500
1599984
Total Time: 00:00:00.1093750
1599985
Total Time: 00:00:00.1093750
1599986
Total Time: 00:00:00.1093750
1599987
Total Time: 00:00:00.1093750
1599988
Total Time: 00:00:00.1093750
1599989
Total Time: 00:00:00.1093750
1599990
Total Time: 00:00:00.1093750
2600000
Total Time: 00:00:00.1718750
2600001
Total Time: 00:00:00.1718750
35000000
Total Time: 00:00:02.2656250
35000001
Total Time: 00:00:02.2656250
35199981
Total Time: 00:00:02.2812500
35199982
Total Time: 00:00:02.2812500
35199983
Total Time: 00:00:02.2812500
35199984
Total Time: 00:00:02.2812500
35199985
Total Time: 00:00:02.2968750
35199986
Total Time: 00:00:02.2968750
35199987
Total Time: 00:00:02.2968750
35199988
Total Time: 00:00:02.2968750
35199989
Total Time: 00:00:02.2968750
35199990
Total Time: 00:00:02.2968750
35200000
Total Time: 00:00:02.2968750
35200001
Total Time: 00:00:02.2968750
500000000
Total Time: 00:00:35.3593750
500000001
Total Time: 00:00:35.3750000
500199981
Total Time: 00:00:35.3906250
500199982
Total Time: 00:00:35.3906250
500199983
Total Time: 00:00:35.3906250
500199984
Total Time: 00:00:35.3906250
500199985
Total Time: 00:00:35.3906250
500199986
Total Time: 00:00:35.3906250
500199987
Total Time: 00:00:35.3906250
500199988
Total Time: 00:00:35.3906250
500199989
Total Time: 00:00:35.3906250
500199990
Total Time: 00:00:35.3906250
500200000
Total Time: 00:00:35.4062500
500200001
Total Time: 00:00:35.4062500
501599981
Total Time: 00:00:35.5000000
501599982
Total Time: 00:00:35.5000000
501599983
Total Time: 00:00:35.5000000
501599984
Total Time: 00:00:35.5156250
501599985
Total Time: 00:00:35.5156250
501599986
Total Time: 00:00:35.5156250
501599987
Total Time: 00:00:35.5156250
501599988
Total Time: 00:00:35.5156250
501599989
Total Time: 00:00:35.5156250
501599990
Total Time: 00:00:35.5156250
502600000
Total Time: 00:00:35.5937500
502600001
Total Time: 00:00:35.5937500
535000000
Total Time: 00:00:37.9218750
535000001
Total Time: 00:00:37.9218750
535199981
Total Time: 00:00:37.9375000
535199982
Total Time: 00:00:37.9375000
535199983
Total Time: 00:00:37.9375000
535199984
Total Time: 00:00:37.9531250
535199985
Total Time: 00:00:37.9531250
535199986
Total Time: 00:00:37.9531250
535199987
Total Time: 00:00:37.9531250
535199988
Total Time: 00:00:37.9531250
535199989
Total Time: 00:00:37.9531250
535199990
Total Time: 00:00:37.9531250
535200000
Total Time: 00:00:37.9531250
535200001
Total Time: 00:00:37.9531250
1111111110
Total Time: 00:01:20.2812500
Start Time: 2006-9-11 2:00:05
End Time: 2006-9-11 2:01:25
Total Time: 00:01:20.2812500
运行结束！