olymmath

Putnam 2020 A2

  • Session A

Let kk be a nonnegative integer. Evaluate ∑j=0k2k−j(k+jj).\sum_{j=0}^k 2^{k-j} \binom{k+j}{j}.

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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