-2⁢ⅈ⁢K⁢k⁢k′⁢sd⁡(2⁢K⁢t,k)=∑n=-∞∞(-1)n⁢πsin⁡(π⁢(t+12-(n+12)⁢τ))=∑n=-∞∞(∑m=-∞∞(-1)m+nt+12-m-(n+12)⁢τ),