Similar to 良設定問題

Dissection problem

Birthday problem

Halting problem

Dirichlet problem

Dubins–Spanier theorems

Knapsack problem

Napkin ring problem

Nim-sum

Hamiltonian path problem

Topswops

Fagnano's problem

Fermi problem

Subset sum problem

Brocard's problem

Class number problem

0.999...

Zero to the power of zero

One-dimensional space

1 + 2 + 3 + 4 + ⋯

1 + 2 + 4 + 8 + ⋯

Root of unity

Ones' complement

1 − 1 + 2 − 6 + 24 − 120 + ⋯

1 − 2 + 3 − 4 + ⋯

1 − 2 + 4 − 8 + ⋯