1n⁢G⁡(m,n)=1n⁢∑k=0n-1ⅇ-π⁢ⅈ⁢k2⁢m/n=ⅇ-π⁢ⅈ/4m⁢∑j=0m-1ⅇπ⁢ⅈ⁢j2⁢n/m=ⅇ-π⁢ⅈ/4m⁢G⁡(-n,m).