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Bala A347854: integrality at every natural index

Abstract

Bala A347854 integrality.

Definition 1.1 (ffact).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.ffact (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

OEIS A347854, COMMENTS (unpaginated): “Fractional factorials are defined using the Gamma function; for example, (n/2)! := Gamma(1 + n/2).” The function ffact uses a real argument.

Definition 1.2 (a).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.a (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

OEIS A347854, NAME (unpaginated): “a(n) = (6n)!/((3n)!(2n)!) * (n/2)!/(3*n/2)!.” Natural factorials are cast to the reals; fractional factorials use ffact.

Definition 1.3 (claim).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.claim (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

OEIS A347854, COMMENTS (unpaginated): “The sequence is conjectured to be integral.” Integrality means that for every natural index, including zero, the value is the cast of an integer.

Theorem 1.4 (mul_div_reduce).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.mul_div_reduce (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

Natural floor division separates a multiple of the quotient from the contribution of the remainder. Nat.div and Nat.mod denote natural division and remainder.

Theorem 1.5 (grid_floor).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.grid_floor (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

When L equals c times the positive integer d, division of the L-scaled numerator and then by d gives the c-scaled quotient. Nat.div denotes natural floor division.

Theorem 1.6 (factorial_prod_dvd_of_floor).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.factorial_prod_dvd_of_floor (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

If every positive-modulus floor sum of B is at most the corresponding sum of A, the product of the factorials in B divides that in A. Nat.div denotes natural floor division. Legendre valuations turn the floor inequalities into divisibility.

Theorem 1.7 (quotient_cast_integral).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.quotient_cast_integral (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

A quotient of natural numbers with a nonzero denominator that divides the numerator is the real cast of an integer.

Definition 1.8 (h856).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h856 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.9 (h856_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h856_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Definition 1.10 (h857).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h857 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.11 (h857_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h857_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Definition 1.12 (h858).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h858 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.13 (h858_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.h858_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Definition 1.14 (k856).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k856 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.15 (k856_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k856_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Definition 1.16 (k857).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k857 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.17 (k857_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k857_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Definition 1.18 (k858).

Formalization. D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k858 (✓ std3).

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The integer-valued floor defect for this factorial ratio. Nat.div denotes natural floor division before the cast to the integers. The associated Landau function occurs in Bober, Table 2.

Theorem 1.19 (k858_nonneg).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.k858_nonneg (✓ std3). ∎

Citation. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

This floor defect is nonnegative at every natural numerator and positive modulus. Reduction modulo the modulus and subdivision at the floor breakpoints gives the inequality.

Theorem 1.20 (gamma_nat).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.gamma_nat (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The Gamma value at one plus a natural number equals its factorial.

Theorem 1.21 (gamma_ratio_half).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.gamma_ratio_half (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

For odd natural r ≤ s, the quotient of the two half-integer Gamma values is a factorial ratio times 2 raised to s−r. Nat.div denotes natural floor division in the factorial arguments.

Theorem 1.22 (gamma_third_ratio).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.gamma_third_ratio (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

Applying the Gamma recurrence n times expresses the third-index quotient as 3 to the power n divided by a product of n positive linear factors.

Theorem 1.23 (even_dvd).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.even_dvd (✓ std3). ∎

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

The denominator of the even-index factorial expression divides its numerator. This supplies both the half-index sequence and the third-index sequence at multiples of three.

Theorem 1.24 (result).

Proof. Machine-checked in Lean as D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.result (✓ std3). ∎

Resolves. Problems/oeis-a347854-bala-half-index-integrality (proved) by D5/S3/Arith/FactorialRatio/OeisA347854BalaHalfIndexIntegral.result.

Source. Repository-derived.

Acknowledgement. Peter Bala (2021). OEIS A347854–A347858: fractional factorial ratios. URL: https://oeis.org/A347854.

Commentary.

Every natural index has an integer value. Reduction to factorial quotients and comparison of prime valuations give an integer cast.

References