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1339 problems

Open problems

Each problem states how progress is verified and what counts as a contribution. Besides the problems curated here, the catalogue includes open conjectures from Formal Conjectures (with Lean statements), optimization constants and the AlphaEvolve problems. Know one that belongs here? Propose a problem.

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A Hard Number theory · Formal Conjectures (Lean)

Unique Crystal Components

If n = ab is a crystal, then there are no other pairs of positive integers c, d > 1, different from the couple a, b, such that n = cd and B(c, d) ∈ ℕ, i.e., the components of the crystals are unique.

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A Hard Logic & formalisation · Formal Conjectures (Lean)

Vaught conjecture

The Vaught conjecture states that for a countable language L and a complete L-Theory T the number of countable models of T (up to isomorphism) is finite, aleph_0 or 2^aleph_0.

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A Hard Graph theory · Formal Conjectures (Lean)

Vizing's conjecture (1968)

Vizing's conjecture (1968). For all finite simple graphs G and H, the domination number of the Cartesian (box) product satisfies γ(G square H) ≥ γ(G) γ(H).

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A Hard Analysis · Formal Conjectures (Lean)

Weak tiling problems

Problem 4.2. Let Ω ⊂ ℝ be a finite union of three or more intervals. If Ω weakly tiles its complement, must it also tile its complement properly?

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A Hard Number theory · Formal Conjectures (Lean)

Wolstenholme numbers

Conjecture: for n > 3, gcd(n, a(n-1)) = A089026(n). - Amiram Eldar and Thomas Ordowski, Jul 28 2019

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A Hard Number theory · Formal Conjectures (Lean)

Wolstenholme Prime

It is conjectured that there are infinitely many Wolstenholme primes. Reference: Wikipedia

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A Hard Number theory · Formal Conjectures (Lean)

Woodall Primes

There are infinitely many prime numbers of the form k * 2 ^ k - 1 for k > 1.

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A Hard Resolved Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 100

WOWII Conjecture 100 (status O): For a simple connected graph G, α(G) ≤ ⌈(max_v l(v) + 0.5 · degreeL2Norm(Gᶜ)) / 2⌉ where α(G) = G.indepNum is the independence number, max_v l(v) is the maximum over all vertices of the independence number of the neighbourhood (in G), and degreeL2Norm(Gᶜ) is the…

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 133

WOWII Conjecture 133: For a simple connected graph G, path(G) ≥ rad(G) + (avg_v l(v))^cC_4(G), where path(G) is the path number of the graph (number of vertices of a largest induced path), rad(G) is the radius (minimum eccentricity, as a natural number), avg_v l(v) = l(G) is the average…

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 189

WOWII Conjecture 189 (status O): For a simple connected graph G, if max_v distEven(v) ≤ 1 + σ(G), then G has a Hamiltonian path. Here distEven(v) is the number of vertices at even distance from v, and σ(G) is the second-smallest degree of G's degree sequence (per WOWII defEntry 65).

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 19

WOWII Conjecture 19 If G is connected then the size b(G) of a largest induced bipartite subgraph satisfies b(G) ≥ FLOOR((∑ ecc(v))/(|V|) + sSup (range (l G))), where ecc(v) denotes eccentricity and l(G) is the independence number of neighbourhoods.

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A Hard Resolved Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 198a

WOWII Conjecture 198a For a simple connected graph G, if b(G) ≤ 2 + ecc_avg(G), then G has a Hamiltonian path. Here b(G) is the number of vertices in a largest induced bipartite subgraph, and ecc_avg(G) is the average eccentricity of G.

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 199

WOWII Conjecture 199 For a simple connected graph G, if tree(G) - 2 ≤ κ(G), then G has a Hamiltonian path. The nontrivial vertex type encodes the source assumption n > 1. Here tree(G) is the number of vertices in a largest induced tree and κ(G) = vertexConnectivity G is the vertex connectivity of G.

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A Hard Combinatorics · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 40

WOWII Conjecture 40 For a nontrivial connected graph G the size f(G) of a largest induced forest satisfies f(G) ≥ ceil((p(G) + b(G) + 1)/2) where p(G) is the path cover number and b(G) is the largest induced bipartite subgraph size.

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 61

WOWII Conjecture 61 For a simple connected graph G, the size f(G) of a largest induced forest satisfies f(G) ≥ residue(G) + ⌈ diam(G) / 3 ⌉, where residue(G) is the Havel-Hakimi residue and diam(G) is the diameter of G.

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 72

WOWII Conjecture 72 For a simple connected graph G, tree(G) ≥ ⌈ecc_avg(G) + max_v λ(v)/3⌉ where tree(G) is the number of vertices in a largest induced tree, ecc_avg(G) is the average eccentricity of G, and max_v l(v) = max_v indepNeighborsCard G v is the maximum over all vertices of the…

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 84

WOWII Conjecture 84 (status O): For a simple connected graph G with positive minimum degree, tree(G) ≥ 2 · rad(G) / δ(G), where tree(G) is the number of vertices in a largest induced subtree, rad(G) is the radius, and δ(G) = G.minDegree is the minimum degree.

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A Hard Graph theory · Formal Conjectures (Lean)

Written on the Wall II - Conjecture 96

WOWII Conjecture 96 For a simple connected graph G on at least two vertices, α(G) ≤ 1 + min_v distEven(v) · (max_v l(v) - 1) where α(G) = G.indepNum is the independence number, distEven(v) is the number of vertices at even distance from v, and max_v l(v) is the maximum independence number of a…

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A Hard Number theory · Formal Conjectures (Lean)

Zagier's Conjecture on Multiple Zeta Values

Zagier's conjecture The ℚ-dimension of the vector space spanned by all multiple zeta values of weight n equals d_n, where d_n is the Zagier dimension sequence satisfying d_0 = 1, d_1 = 0, d_2 = 1, and d_n = d_n-2 + d_n-3 for n ≥ 3.

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A Hard Resolved Algebra · Formal Conjectures (Lean)

Zariski Cancellation

The Zariski Cancellation Problem: every polynomial ring over a field k of characteristic 0 is cancellative.

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