Erdős Problem a Daythe open tracker

Erdős Problem #264

OPENdatabase updated 2025-08-31

No proof or disproof is known, and it isn't known whether a finite computation could settle it.

What the community database records, not our verdict. erdosproblems.com no longer shows statuses (why).

A sequence \(a_n\) of integers is called an irrationality sequence if for every bounded sequence of integers \(b_n\) with \(a_n + b_n \neq 0\) and \(b_n \neq 0\) for all \(n\), the sum \[ \sum \frac{1}{a_n + b_n} \] is irrational. Note: there are other possible definitions of this concept. See FormalConjectures/ErdosProblems/263.lean for another possible definition.

Is \(2^n\) an example of an irrationality sequence? Kovač and Tao proved that it is not [KoTa24] [KoTa24] Kovač, V. and Tao T., On several irrationality problems for Ahmes series. arXiv:2406.17593 (2024).
Statement as formalized in Formal Conjectures (Google DeepMind, Apache-2.0) · their label: research solved · 4 further variants / known partial results in the Lean file. The authoritative wording is on erdosproblems.com/264.
Prizenone
Topicsirrationality
Statement in LeanFormal Conjectures
Solution in Leanno
Original pageerdosproblems.com/264
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Proved fixed-bound factorial-tail separation and Hausdorff dimension zero, reduced a positive factorial answer to open problem #68, and exactly certified that every rational sum for all admissible $\{

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