olymmath

Putnam 2020 B1

  • Session B

For a positive integer nn, define d(n)d(n) to be the sum of the digits of nn when written in binary (for example, d(13)=1+1+0+1=3)d(13) = 1+1+0+1=3). Let S=∑k=12020(−1)d(k)k3.S = \sum_{k=1}^{2020} (-1)^{d(k)} k^3. Determine SS modulo 2020.

Curated text Kedlaya Putnam archive. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.

Add a solution

Locator putnam/2020/b1 · Tag M4T85XGE6M · Edit this page on GitHub · Keys: j next, k previous