∑∞n=-∞f⁡(x+n)=∑∞n=-∞ⅇ2⁢π⁢ⅈ⁢n⁢x⁢∫-∞∞f⁡(t)⁢ⅇ-2⁢π⁢ⅈ⁢n⁢t⁢ⅆ⁡t.