======∑i=1n∑j=1nf(ij)∑i=1n∑j=1n∑d=1n2[dgcd(i,d)|j]∑i=1n∑d=1n2⌊n∗gcd(i,d)d⌋∑d=1n∑i=1⌊nd⌋∑j=1⌊n2d⌋⌊nj⌋e(gcd(i,j))∑d=1n∑i=1⌊nd⌋∑j=1n⌊nj⌋∑x|gcd(i,j)μ(x)∑x=1nμ(x)∑d=1n⌊ndx⌋∑j=1⌊nx⌋⌊njx⌋∑x=1nμ(x)(∑j=1⌊n