Suppose person A collaborated with person B, who has collaborated with person C, who has collaborated with Paul Erdös. Suppose also that person B never collaborated with Paul Erdös and person A never collaborated with anyone with an Erdös number of 1 or less. What is person A’s Erdös number?

The numbers are surely

C:1
B:2
A:3

To determine person A's Erdös number, we need to analyze the information given about their collaborations and the collaborations of others.

According to the given information:
- Person B collaborated with person C, who collaborated with Paul Erdös.
- Person B never collaborated with Paul Erdös.
- Person A never collaborated with anyone with an Erdös number of 1 or less.

By analyzing this information, we can infer the following:
- Person B has an Erdös number of 2 since they collaborated with person C, who collaborated with Paul Erdös.
- Person A collaborated with person B, so their collaboration can contribute to their Erdös number.

Since Person A never collaborated with anyone with an Erdös number of 1 or less, and Person B has an Erdös number of 2, it implies that Person A's Erdös number is 3.

Therefore, Person A's Erdös number is 3.