Hey Gustavo,

Please read the definition of Erdős number carefully.

"Erdős number one corresponds with the person who has published a paper with Erdős and Erdős number two with the one who has published a paper with the collaborator of Erdős".

Now, Hardy was a collaborator of Erdős with Erdős number of 2 and Ramanujan was the student of Hardy.

Cheers.

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