slug: oeis-a395531-greedy-brick-all-index bibkey: udovenko2026a395531 doi: null url: https://oeis.org/A395531/internal triage: theorem motivation_gids:

• D5/S3/Combinatorics/GreedyBrick/OriginalIdentity

The greedy-brick all-index identity

Problem

OEIS A395531, revision 30, Aleksei Udovenko:

Conjecture: when n = a(m) for some m, we have a(n) = n(n+3)/2 - m. Verified experimentally up to m=1172, n=688491.

Rows are numbered from one. The value a(m) is the width of the first brick in row m under the literal highest-supported-row placement rule. The exact assertion is a(a(m)) = a(m)(a(m)+3)/2-m for every integer m >= 1.

Motivation

This first-tier externally named conjecture asks for an identity at every positive index. Totality and correspondence to actual row births are part of its meaning.

Gap

The source entry still labels the assertion a conjecture. The bounded literature scope recorded in issue 11600 covers all thirty entry revisions, the linked optimized generator, related entries, jOEIS and OEIS-Python, identifier searches on arXiv and Crossref, and bounded GitHub Lean searches. No published resolution was found in that scope. The frozen predecessor, band and trace declarations do not state the original all-index identity; the pinned Mathlib search supplied no matching theorem.

Route

The literal capacity trajectory has a least birth for every positive row. An initialized cofinal rest trace samples that same trajectory. The local block-prefix induction proves that height stays constant strictly before the final brick of each rest block. Thus the least literal birth of row m is precisely the endpoint of the event birth of m.

Write b(m) for that endpoint. The frozen successor band gives the exact cut: a renewal f lies before birth b(m) if and only if its predecessor lies before birth m. The frozen successor inverse laws turn this into a weight-preserving bijection. Endpoint increments telescope to bin weights. Births through height b(m) contribute b(m)(b(m)+1)/2; renewals contribute b(m)-m. Their sum is b(m)(b(m)+3)/2-m, and the birth correspondence gives the original literal-sequence identity.

Falsifier

A positive m for which both actual births exist and the displayed identity fails would refute the assertion. No matching finite prefix is used as proof. The chronological-word-copy counterexample at brick 242 rejects a stronger route, while the raw EventLaws countermodel lacks the actual rest-trace hypotheses; neither is a counterexample to this assertion.

Evidence

The mathematical source is D5/S3/Combinatorics/GreedyBrick/OriginalIdentity.lean. Its sole theorem result quantifies over every m >= 1 and assumes no trace, recurrence, cut law or new birth premise. Its axiom closure is propext, Classical.choice and Quot.sound. The definition a uses the already proved least literal birth at positive indices; its unused zero value is zero.

Triage

Proved in the local proof of D5/S3/Combinatorics/GreedyBrick/OriginalIdentity.result: the strict-prefix property of first-zero blocks connects event births to physical births, and the predecessor bijection preserves renewal weights without requiring chronological order of renewal labels. The event identity is also proved there for every initialized unbounded RestTrace.

Open: extensions to other placement rules require their own literal birth correspondence.

Source evidence: no dependent theorem or follow-up question relying on the conjecture was identified in the inspected original OEIS entry.

ASSUMED-UNVERIFIED

The bounded source search does not establish first-publication priority. The source-to-Lean interpretation uses the frozen row-scan and common labelled-history correspondence. The linked optimized generator’s license has not been verified, and its source is not redistributed.