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I want a bijective map from $\bf N \times N$ to $\bf N$. I can think of injective map easily. But, bijective seems to be hard to think.

Asaf Karagila
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    This has been asked here before. The diagonal argument is the usual way to do this, that is $(1,1),(1,2),(2,1),(3,1),(2,2),(1,3),\ldots$ – Pedro Aug 14 '13 at 01:33
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    With over a thousand points at your disposal, I expect you to be able and use the search function of the site and show a little more effort in searching before posting questions. – Asaf Karagila Aug 14 '13 at 01:35
  • http://math.stackexchange.com/questions/120393/construct-a-bijection-between-mathbbz-times-mathbbz-and-mathbbz and http://math.stackexchange.com/questions/54158/the-cartesian-product-mathbbn-times-mathbbn-is-countable and http://math.stackexchange.com/questions/16611/bijecting-a-countably-infinite-set-s-and-its-cartesian-product-s-times-s and there are probably a few more. – Asaf Karagila Aug 14 '13 at 01:37
  • Take a look in my question here: http://math.stackexchange.com/questions/427212/do-i-need-to-present-a-formula-in-this-proof I think it can help you out. – Gold Aug 14 '13 at 01:38
  • A more general question: http://math.stackexchange.com/questions/278679/does-anyone-know-a-closed-form-expression-for-a-bijection-between-mathbbnk/395080#395080 – João Alves Jr. Aug 14 '13 at 01:40

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