'SQL - Distribution Count

Hi I have the following table:

 crm_id  | customer_id

jon         12345
jon         12346
ben         12347
sam         12348

I would like to show the following:

Crm_ID count | Number of customer_ids
1                    2
2                    1

Basically I want to count the number crm_ids that have 1,2,3,4,5+ customer_ids.

Thanks

sql

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