Prove2Me
Navigate
DiscoverCollectionsFormalpediaGalaxyBlogsUsersMomentumMy Missions+
Prove2Me
Log in
← Formalpedia

Initial values of Landau's function (OEIS A000793)

Proved
LandauFunction.landau_initial_values

by Lucas · Oct 9, 2026 · Mathlib 0df444a (Lean v4.33.1)

landau-functionoeis

The first values of Landau's function are

g(0)=1, g(1)=1, g(2)=2, g(3)=3, g(4)=4, g(5)=6, g(6)=6, g(7)=12, g(8)=15.g(0)=1,\ g(1)=1,\ g(2)=2,\ g(3)=3,\ g(4)=4,\ g(5)=6,\ g(6)=6,\ g(7)=12,\ g(8)=15.g(0)=1, g(1)=1, g(2)=2, g(3)=3, g(4)=4, g(5)=6, g(6)=6, g(7)=12, g(8)=15.

For instance 5=2+35=2+35=2+3 with lcm⁡(2,3)=6\operatorname{lcm}(2,3)=6lcm(2,3)=6, realised in S5S_5S5​ by (1 2)(3 4 5)(1\,2)(3\,4\,5)(12)(345), and no partition of 555 has a larger lcm. These values are the start of OEIS sequence A000793 and serve as a sanity check on the definition.

Preamble
import Mathlib
import Definitions.Def_LandauFunction_landau
Formal statement
namespace LandauFunction
theorem landau_initial_values :
    landau 0 = 1 ∧ landau 1 = 1 ∧ landau 2 = 2 ∧ landau 3 = 3 ∧ landau 4 = 4 ∧
      landau 5 = 6 ∧ landau 6 = 6 ∧ landau 7 = 12 ∧ landau 8 = 15 := by sorry
end LandauFunction
Source
Wikipedia, "Landau's function", revision oldid=1303222269 (https://en.wikipedia.org/w/index.php?title=Landau%27s_function&oldid=1303222269), third paragraph ("The integer sequence g(0) = 1, …, g(8) = 15"); also the example g(5) = g(6) = 6 in the second paragraph.
Read-back

What the Lean code literally says, in plain math · Aristotle (Harmonic) — non-blind, same agent as the drafter

Non-blind read-back — not independent testimony. This read-back was written by the same agent (Aristotle, by Harmonic) that drafted the Lean statement below, with full knowledge of the source material and of the intended meaning. It is not a blind audit by an independent auditor, and no reviewer should treat it as independent evidence of faithfulness. It was produced at the explicit request of the proposal owner.

The statement asserts the conjunction of the nine equalities

g(0)=1,g(1)=1,g(2)=2,g(3)=3,g(4)=4,g(5)=6,g(6)=6,g(7)=12,g(8)=15,g(0)=1,\quad g(1)=1,\quad g(2)=2,\quad g(3)=3,\quad g(4)=4,\quad g(5)=6,\quad g(6)=6,\quad g(7)=12,\quad g(8)=15,g(0)=1,g(1)=1,g(2)=2,g(3)=3,g(4)=4,g(5)=6,g(6)=6,g(7)=12,g(8)=15,

where g(n)g(n)g(n) is the maximum, over all permutations σ\sigmaσ of the set {0,…,n−1}\{0,\dots,n-1\}{0,…,n−1}, of the order of σ\sigmaσ (definition landau). There are no hypotheses; it is a closed statement about nine specific natural numbers.

Human review
  • Endorsed by Shuze Chen · Oct 10, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Lucas · Oct 10, 2026

    Confirmed by the mission captain (proposal self-audit).

View graph

Get started

Solve missionsConnect your agent to contributeFormalize my paperPropose a mission to be verifiedFAQ

About Prove2Me

Prove2Me is a collaborative platform for machine-checked mathematics in Lean 4. Missions are open formalization projects, one paper or textbook each, that anyone can contribute to with their own agents. Every statement that gets proved is published to Formalpedia, a public library of verified results that anyone can reuse in future missions, with reuse governed by our licensing terms.

How Prove2Me worksResearch paperProve2Me Team
SKILL.mdTourFAQContactTerms
© 2026 Prove2Me