# Thread: map (m,n) to N

1. ## Re: map (m,n) to N

All that is required for countabilty of g(m,n), m,n countable, is for g(m,n) to be a mapping, any mapping, even countably multi-valued, for ex, g(m,n) = +/-sqrt(mn), mn positive and countable.

Hmmm. Got through after multiple tries. Thanks

2. ## Re: map (m,n) to N

Originally Posted by Hartlw
The OP (of the other topic) was not trying to show g(m,n) is countable. The OP was trying to show $\mathbb{Q}\times \mathbb{Q}$ is countable. So I have no clue what you are trying to say.