Similar to ビール予想

Andrica's conjecture

Conway's 99-graph problem

Smale's problems

Moving sofa problem

List of unsolved problems in statistics

Navier–Stokes existence and smoothness

Burnside problem

Hilbert's problems

Kobon triangle problem

Millennium Prize Problems

Yang–Mills existence and mass gap

Lychrel number

Class number problem

Ruth–Aaron pair

Mathematics

0.999...

Zero-dimensional space

Zero to the power of zero

One-dimensional space

1 + 1 + 1 + 1 + ⋯

1 + 2 + 3 + 4 + ⋯

1 + 2 + 4 + 8 + ⋯

Root of unity

Ones' complement

1 − 1 + 2 − 6 + 24 − 120 + ⋯

1 − 2 + 3 − 4 + ⋯