ζ⁡(s,a)=12⁢a-s+a1-ss-1+∑k=1nΓ⁡(s+2⁢k-1)Γ⁡(s)⁢B2⁢k(2⁢k)!⁢a-2⁢k-s+1+1Γ⁡(s)⁢∫0∞(1ⅇx-1-1x+12-∑k=1nB2⁢k(2⁢k)!⁢x2⁢k-1)⁢xs-1⁢ⅇ-a⁢x⁢ⅆ⁡x,