Putnam 2025 B3

Session B

Suppose $S$ is a nonempty set of positive integers with the property that if $n$ is in $S$ , then every positive divisor of $2025^n -15^n$ is in $S$ . Must $S$ contain all positive integers?

Curated text Kedlaya Putnam archive. Quoted with source.

Solutions

Human solution Solution 1 by Manjul Bhargava, Kiran Kedlaya and Lenny Ng

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