Proving Cardinality

Hello,
Urgently need some help with some Mathematical Communication.
The question is:
Show that the set of all odd square numbers {1,9,25,49,...} has cardinality ℵ0 [aleph-zero].

Any ideas? (Worried)

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Originally Posted by Ellis

Show that the set of all odd square numbers {1,9,25,49,...} has cardinality ℵ0 [aleph-zero].

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The -th non-negative odd number is ...

Can you use this to find a bijection which maps onto ?

What is the largest cardinality, because surely I can start with the cardinality of the set of all Real numbers and then work from there?

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Originally Posted by Ellis

What is the largest cardinality

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I don't know.

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because surely I can start with the cardinality of the set of all Real numbers and then work from there?

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I don't think so.