Is there a tool or website to compile a program on their server, without having to stay in the window, I want for example to write a program that counts from 1 to 10^10, and I might want to close the window and get back to it later, after it finished. like the compilation is done in the server.

Is there an efficient way to calculate the sum of lcm(x,y) for every value x and y such that 1<=x<=n && 1<=y<=n with a given n ?