[Formal proof in progress] OEIS A147983 Chomp 10x42

[DomTheDeveloper]

Superseded by #185.

The authoritative computational artifact is stored on the dedicated DomTheDeveloper/formal-conjectures branch proof-artifacts/oeis-a147983-chomp:

https://github.com/DomTheDeveloper/formal-conjectures/tree/a0c8858ce9b22166d0616931ea1fc996e335b03d/ProofArtifacts/OEIS/A147983

The clean submission remains two commits, one changed Lean file, and zero commits behind the recorded Google DeepMind base.

[github-actions]

👋 This is an automated welcome message. 🤖
Thanks for the contributions!

A few friendly reminders while the review gets started:

• Please take a look at the style guidelines,
  especially the conventions for references, categories, AMS tags, and answer(sorry).
• You can manage some PR labels by leaving a comment with +label-name or -label-name; for example, +awaiting-author or -awaiting-author.
• This repository is mainly for formalised statements. Proofs longer than about 25-50 lines are usually out of scope; longer proofs are welcome to be included/linked via the formal_proof mechanism.

Thanks again for helping improve Formal Conjectures.