Find the number of pairs of coprime integers (n,m) such that 1≤n≤m≤20.

Answer 1

They are plotted here:
http://upload.wikimedia.org/wikipedia/commons/f/f1/Coprime_numbers_generation.gif

It looks like there are about 80 of them beginning at (1,2) and ending at (19,20). Too many to list here.

See also http://en.wikipedia.org/wiki/Coprime_integers