Ordered ways to write 2n = p + q with p, q and p_p+2 + 2 all prime

Conjecture: (i) a(n) > 0 for all n > 2.

From the catalogue. Imported from The Formal Conjectures Authors (Google DeepMind and contributors) (Apache-2.0) — original. Nobody has started on it here yet: tasks are created as soon as someone asks for one or submits a claim.

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Cite

@misc{cairn-oeis-236566,
  title        = {Ordered ways to write 2n = p + q with p, q and p_p+2 + 2 all prime},
  author       = {{Cairn Commons contributors}},
  howpublished = {\url{https://cairn-commons.com/problems/oeis-236566}},
  year         = {2026},
  note         = {Open problem on Cairn Commons, CC BY 4.0. Accessed 2026-11-11}
}

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Claims

Verified

Disputed

Refuted

On the literature board

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What a result looks like: C-16, a newcomer working with an AI model found C(85,24,3) ≤ 76 (previous best 77), and a computer verified it within minutes. A documented dead end counts too.

The problem

The question

conjecture_1. Conjecture: (i) $a (n) > 0$ for all $n > 2$ .

conjecture_2. Conjecture: (ii) If $n > 30$ , then $2 n + 1$ can be written as $2 p + q$ with $p$ , $q$ and $prime (p + 2) + 2$ all prime.

Let $p_{k}$ denote the $k$ -th prime number. The sequence $a (n)$ counts the number of ordered ways to write $2 n = p + q$ with $p, q$ , and $p_{p + 2} + 2$ all prime.

Formal statement (Lean 4)

From Formal Conjectures, module FormalConjectures.OEIS.«236566» (2 statements).

theorem conjecture_1 (n : ℕ) (hn : 2 < n) : 0 < a n

theorem conjecture_2 (n : ℕ) (hn : 30 < n) :
    ∃ p q : ℕ, p.Prime ∧ q.Prime ∧ (Nat.nth Nat.Prime (p + 1) + 2).Prime ∧
      2 * n + 1 = 2 * p + q

What counts as progress

A Lean proof of one of the statements above, pinned as the claim's formal statement.
Partial results: special cases, weaker bounds, reductions — as verified claims.
Computations and numerical evidence with published code (reproducible).
Literature: the problem may have been solved or partly solved already. Report it as a literature claim.
A precise flaw in the formal statement (a misformalisation) — report it upstream too.

References

A236566

Source and licence

Imported from Formal Conjectures (OEIS), commit 2f91d251c07f. Statements and descriptions © The Formal Conjectures Authors, Apache License 2.0; reformatted for this page.