Problems

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

Estimate the number F(x) of minimal distinct covering systems whose moduli all lie in [1, x]. The candidate proof gives loglog F(x)/log x → 1, i.e. F(x) = exp(x^1+o(1)).

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

Let M(n) be the supremum of ∑_a ∈ A 1/(n-a) over pairwise coprime A ⊂ [1,n). Erdos asked whether M(n) ≤ ∑_p<n 1/p + O(1) uniformly. The average order is settled: ∑_n ≤ N M(n) = e^-γ N loglog N + O(N).

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

If g_3(n) is the largest size of A ⊆ [1,n] with fewer than three representations of every product a_1 a_2, does its conjectured second-order normalized term converge? The candidate proof gives an explicit limit constant.

Let A⊂N be infinite. Must there exist some k≥ 1 such that almost all integers have a divisor of the form a+k for some a∈ A? The question as posed follows negatively from Davenport–Erdős (1951). The AI result settles Tenenbaum's harder…

Does the block 11 occur infinitely often in the base-2 expansion of the Erdős-Borwein constant E = ∑_n ≥ 1 1/2^n - 1? Posed by Crandall in 2012.

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

Does the sum of the reciprocals of all primitive pseudoperfect numbers converge?

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

If each integer has at most r representations m = pa with p prime and a ∈ A ⊆ [1, N], what is the best upper bound for ∑_a ∈ A 1/a? The candidate proof gives the matching order Θ_r(log N / loglog N).

Define φ_k(n) = ∑_1 ≤ a ≤ n, (a,n)=1 a^k and D_s = k ≥ s : φ_s(n) | φ_k(n) for every n. Is D_1 = 1, 3, 15, as conjectured by Büyükaşik and collaborators?

Let a,b,c>1 be pairwise coprime integers. Is every large integer a sum of distinct numbers of the form a^k b^l c^m (k,l,m≥ 0), none dividing another?

Let F(N) be the maximal size of A⊆1,…,N such that no a∈ A divides the sum of any nonempty subset of A∖a. Estimate F(N). The lower bound F(N)≫ N^1/5 is classical, from constructions of Erdős and Csaba, and every non-dividing set is…

VibeMathed records no statement for this problem. See erdosproblems.com for the original.

Erdős conjectured, in over a dozen papers spanning 1976 to 1997 and with a $1000 prize attached, that every finite Sidon set extends to a perfect difference set modulo p^2+p+1 for some prime p. Alexeev and Mixon establish that 1,2,4,8 is a…