oeis-a381423-hermite-differences - trureturing

Metadata

slug: oeis-a381423-hermite-differences
bibkey: sheppard2025a381423
doi: null
triage: theorem
motivation_gids:
  - D5/S3/Analytic/Polynomial/HermiteSignedMode.result
url: https://oeis.org/A381423/internal

Problem

OEIS A381423 revision 8, Mike Sheppard, has the independent conjecture clause: “Differences are either 1 or -3”. Its full comment continues with finer patterns, spacing and square-root growth. The independent target is preregistered at #25634.

For every natural n, including zero, let a(n) be the smallest j in zero through n maximizing the signed coefficient of $x^{j}$ in the physicists Hermite polynomial $H_{n}$ . The exact assertion is

$(a (n + 1) : Z) - (a (n) : Z) = 1 or - 3.$

The source’s Mathematica first PositionLargest and PARI upward scan establish the tie convention. Its n=5 example selects exponent 1, distinguishing signed order from absolute coefficient order.

Statement echo

Source clause	Lean counterpart
Physicists H_n	`physicistsHermite n`, the literal DLMF 18.5.13 finite factorial expansion over ℚ.
Coefficient at exponent j	`polynomial_coeff` proves extraction equals `signedCoeff n j` throughout zero through n.
Signed maximum	`IsSmallestMax` compares rational coefficients directly, with no absolute value.
Smallest tied exponent	The last conjunct of `IsSmallestMax`; the proof chooses the largest positive-term index.
Every n, including zero	Unrestricted `∀ n : ℕ` in both conjuncts of `claim`.
Integer difference	Both values of `a` are cast to ℤ before subtraction.
No uniqueness assumption	No assumption is present; all tied maximizers enter the selector predicate.

Motivation

Alternating signs restrict a positive signed maximum to exponents congruent to n modulo four. Their adjacent coefficient ratios identify a threshold that moves by at most one lattice site when n increases by one.

Gap

The supplied research screen found no exact settlement in its inspected OEIS/DLMF material, the bounded portions of Bonneux–Dunning–Stevens arXiv:1909.03874v2, or Dudeja–Hsu Lemma 35. The latter concerns a normalized absolute coefficient bound. No global openness or priority claim follows.

The local statement search covered public and private D5 Hermite declarations, the corresponding theory sources and pinned Mathlib at 56a005855ea17e0b0958f73ec801ae140b0a1679. Mathlib’s explicit Hermite formulas use probabilists normalization. Existing Jensen top-coefficient suppliers also use that convention; no private exposure is required for this proof. Bounded GitHub Lean searches for A381423, Hermite argmax and Hermite unimodal returned zero code hits. These are bounded searches, not exhaustive ecosystem or literature coverage. Generic finite extrema and factorial identities are reused; no exact matching transition theorem was found in the searched scope.

Route

Set $j = n - 4 r$ and

$w (n, r) = \frac{2 ^{n - 4 r}}{( 2 r )! ( n - 4 r )!}, 4 r \leq n .$

The signed coefficient at this exponent is $n! w (n, r) > 0$ . Every other coefficient is nonpositive. The exact adjacent relation, whenever $4 (r + 1) \leq n$ , is

$w (n, r + 1) 16 (2 r + 2) (2 r + 1) = w (n, r) (n - 4 r) (n - 4 r - 1) (n - 4 r - 2) (n - 4 r - 3) .$

Define the threshold predicate at r by

$4 r \leq n, 16 (2 r) (2 r - 1) \leq (n - 4 r + 1) (n - 4 r + 2) (n - 4 r + 3) (n - 4 r + 4) .$

Zero satisfies it. Its true indices form an initial segment: the left side increases with r and the right side decreases. Let m(n) be the largest true index. For r at most m(n), the weights rise weakly; past m(n), they fall strictly. Induction gives global maximality and strict exclusion of every larger r. Thus $a (n) = n - 4 m (n)$ is precisely the smallest exponent among signed maximizers, including any ties.

Every true threshold for n remains true for n+1. Conversely, a true threshold at r+1 for n+1 implies a true threshold at r for n: its left side decreases, and the right-side argument increases by three. Hence $m (n) \leq m (n + 1) \leq m (n) + 1$ . Substituting into $a (n) = n - 4 m (n)$ proves the integer difference assertion for all n. The endpoint constraints make each natural subtraction agree with ordinary subtraction in these calculations.

Falsifier

A natural n and the two actual smallest signed maximizers with integer difference outside {1,-3} would refute the assertion. Finite testing, an absolute coefficient selector, a probabilists polynomial, or a uniqueness assumption would not establish this target.

Evidence

HermiteSignedMode.result : claim includes both the exact selector certificate and the universal difference assertion.

The source-owner Reg mirror observes the complete natural sequence. Its law preserves the selector and every integer difference. The constant-zero family violates the difference law at zero and supplies whole-family variation and one-role sensitivity. The actual sequence has different observations at zero and one, directly from the proved nonzero difference. Continuation is unknown; no undecidability or inexhaustibility conclusion follows.

Triage

Proved: the threshold mechanism gives a rightmost positive-term mode whose index moves by zero or one; the smallest maximizing exponent therefore moves by one or minus three. This proof handles ties without settling their absence. The coefficient formula defines the actual physicists polynomial directly; no unproved invariance of argmax under rescaling is used.

Unresolved and outside this independent target: the fine patterns (1,1,1,-3) and (1,1,1,1,-3), their proposed spacing, square-root asymptotics, and the source’s separate uniqueness assertion. No dependent source theorem requiring these finer assertions is established by this result. The threshold method suggests related mode interlacing questions, which require separate statements and eligibility decisions.

ASSUMED-UNVERIFIED

Literature completeness and global priority remain unverified because the source screen is bounded. The unknown audit continuation supplies no further mathematical conclusion.

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