查看原题'" class='mdui-btn mdui-btn-raised'>点击加载点击跳转$$f=\sum{i=1}^{a}\sum{j=1}^{b}[gcd(i,j)=d]\f=\sum{i=1}^{\left \lfloor \frac ad \right \rfloor} \sum{j=1}^{\left \lfloor \frac bd \right \rfloor} [gcd(i,j)=1]\\because \sum{x|n} \mu(x) = [n=1]\\therefore f= \sum{i=1}^{\left \lfloor \frac ad \right \rflo……