How to compute this GCD Sum?

Revision en1, by -synx-, 2017-07-09 17:09:55

I have been trying to solve this problem for past 2 days, but I havent come up with a formal solution.

I have tried to change the order of sums and grouping by gcd but couldnt get any further than getting a bound on distinct values of gcd .
Can someone please help?
Source: PE 530

Tags gcd, projecteuler


  Rev. Lang. By When Δ Comment
en1 English -synx- 2017-07-09 17:09:55 503 Initial revision (published)