The meaning of problems
Known \ (n-, m \) , seeking \ (\ SUM N_A ^ \ ^ M_B SUM D (ab &) \) , where \ (d (x) \) represents \ (X \) number of divisors.
Thinking
Conclusion: \ (D (I, J) = \ I sum_ {|} n-\ sum_ {J | m} [GCD (I, J) ==. 1] \) . (See below prove)
Whereby available is equivalent to the original formula \ (\ sum ^ n_a \ sum ^ m_b \ sum_ {i | n} \ sum_ {j | m} [gcd (i, j) == 1] \)
即\(\sum^n_i\sum^m_j\frac{n}{i}\frac{m}{j}[gcd(i,j)==1]\)