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One problem that I found quite interesting is the Hadwiger-Nelson problemHadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
Edit: The chromatic number is now known to be at least 5.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
Edit: The chromatic number is now known to be at least 5.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
Edit: The chromatic number is now known to be at least 5.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
Edit: The chromatic number is now known to be at least 5.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
Edit: The chromatic number is now known to be at least 5.
One problem that I found quite interesting is the Hadwiger-Nelson problemHadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
One problem that I found quite interesting is the Hadwiger-Nelson problem for coloring the plane. The proofs that the answer is at most $7$ and at least $4$ are easy and elegant (but also quite different), and it has the added bonus that it is an open problem.
