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Sierpiński number

The extended Sierpiński problem.* Is 271129 the second-smallest Sierpiński number?

Mathematical statement

The extended Sierpiński problem.* Is 271129 the second-smallest Sierpiński number?

Even if 78557 is confirmed as the smallest Sierpiński number, there could exist a composite Sierpiński number kk with 78557<k<27112978557 < k < 271129. We formalize "second-smallest" as: the least Sierpiński number kk such that there exists exactly one Sierpiński number below it.

Statement source: Wikipedia statement material

Statement terms: CC-BY-SA-4.0

Attributed source material. Reuse must follow the linked attribution and share-alike terms.

Statement artifacts, not proofs

These records expose exact Lean propositions and statement-only wrappers. Defining a proposition does not supply a proof of it. A placeholder-bearing target also contains no proof. Elaboration checks syntax and types; it does not certify that a formalization perfectly captures every nuance of the informal problem.

Pinned Lean formulation 1

extended_sierpinski_problem

Canonical source
Complete statement target, proof intentionally absentLean 4
theorem extended_sierpinski_problem :    answer(sorry)       IsLeast {k | k.IsSierpinskiNumber          k', k'.IsSierpinskiNumber  k' < k} 271129 := by  sorry
Statement source
Formal Conjectures
Lean version
v4.27.0
Placeholder
Present; no proof artifact
Source evidence
Pinned source index
Fidelity review
Community formulation

References