olymmath

Putnam 2021 A5

  • Session A

Let AA be the set of all integers nn such that 1≤n≤20211 \leq n \leq 2021 and gcd⁡(n,2021)=1\gcd(n, 2021) = 1. For every nonnegative integer jj, let S(j)=∑n∈Anj.S(j) = \sum_{n \in A} n^j. Determine all values of jj such that S(j)S(j) is a multiple of 2021.

Curated text Kedlaya Putnam archive. Quoted with source.

Solutions

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

The terms of the source let olymmath link to this solution but not copy it. Read the solution (Kedlaya Putnam archive).

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