Help with rational numbers?

Question 1:
How many distinct rational numbers p/q exist, when p and q are positive integers, p <= q, and q <= N, where N is a given natural number?

Question 2:
What is the next greater such number from a given rational number r/s with the same properties?

q          p/q such that p <= q
1          1/1
2          1/1 1/2 2/2
3          1/1 1/2 2/2 1/3 2/3 3/3
4          1/1 1/2 2/2 1/3 2/3 3/3 1/4 2/4 3/4 4/4
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