∑j=anf⁡j=∫anf⁡x⁢ⅆ⁡x+12⁢f⁡a+12⁢f⁡n+∑s=1m-1B2⁢s2⁢s!⁢f2⁢s-1⁡n-f2⁢s-1⁡a+∫anB2⁢m-B~2⁢m⁡x2⁢m!⁢f2⁢m⁡x⁢ⅆ⁡x.