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Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

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Source: published paper, printed p. 413 (PDF p. 3), the proof of Theorem 2. The source reports a Maple evaluation checked with GP/PARI, but does not supply its program. The independent implementation here evaluates an elementary upper bound for the same expression.

Certified statement and replay

Use

b=50,m=18,δ=0.947265625⋅10−8=9710240000000.b=50,\quad m=18,\quad \delta=0.947265625\cdot10^{-8}=\frac{97}{10240000000}.

The exact root AA from Theorem 1 lies in

545439823.214<A<545439823.216.545439823.214<A<545439823.216.

The certificate proves every domain condition of that theorem, shows Y=AY=A and A′>1A'>1, and gives an upper bound ε^\widehat\varepsilon on its error constant with

ε≤ε^<1812000000000=0.905⋅10−7.(1)\varepsilon\le\widehat\varepsilon< \frac{181}{2000000000}=0.905\cdot10^{-7}. \tag{1}

The upper-bound expression is approximately 9.049931514⋅10−89.049931514\cdot10^{-8}. This decimal is illustrative only; the strict comparison in (1) is performed on integers.

The parameter file and standard-library checker make the calculation portable. From the repository root:

bash
uv run --no-sync python library/primes/dusart_1999_kth_prime_lower_bound/evidence/verify_dusart1999.py --output library/primes/dusart_1999_kth_prime_lower_bound/evidence/output/dusart1999_replay.json

The script also works from another directory when its absolute path is used; the optional output path above lies in the owner's ignored evidence/output/, and without it nothing is written. Stdout carries one line per named obligation and a summary line before the JSON, whose exit_code equals the process exit status; any failed obligation exits nonzero, including under python -O. The interval arithmetic uses only Python's standard library, with the check harness from the root tools package of the repository environment; the script neither runs downloaded author code nor builds a proof assistant. Expected runtime is about one second.

Full computer-assisted proof

Let S=21024S=2^{1024}. The integer pair [l,u][l,u] represents the real interval [l/S,u/S][l/S,u/S]. A rational number rr is enclosed by [⌊Sr⌋,⌈Sr⌉][\lfloor Sr\rfloor,\lceil Sr\rceil]. Addition and subtraction use the appropriate endpoints. Multiplication takes the minimum and maximum of the four endpoint products and rounds outward. Division does the same with the four endpoint quotients after checking that the denominator interval is positive. These operations remain valid for signed numerators.

For a nonnegative argument, the integer-root routine returns vv only after verifying vm≤n<(v+1)mv^m\le n<(v+1)^m. Applying that check to n=lSm−1n=lS^{m-1} and n=uSm−1n=uS^{m-1} supplies an enclosing interval for an mmth root. No approximate root is accepted without these exact inequalities.

The transcendental evaluations also have explicit rational remainders:

  • Write a positive logarithm argument as 2jy2^j y with 1≤y<21\le y<2, using integer comparisons. For z=(y−1)/(y+1)z=(y-1)/(y+1),
log⁡y=2∑r≥0z2r+12r+1.\log y=2\sum_{r\ge0}\frac{z^{2r+1}}{2r+1}.

After NN terms the omitted sum is at most 2z2N+1/[(2N+1)(1−z2)]2z^{2N+1}/[(2N+1)(1-z^2)]. The same formula at z=1/3z=1/3 encloses log⁡2\log2. The checker uses N=400N=400, keeping the remainder even when it is smaller than one interval unit.

  • Normalize a nonnegative exponential argument by powers of two so it lies in [0,1/8][0,1/8]. After the Taylor terms through degree NN, its positive remainder is at most
xN+1(N+1)!11−x/(N+2).\frac{x^{N+1}}{(N+1)!}\frac1{1-x/(N+2)}.

The ratio bound follows because all subsequent term ratios are at most x/(N+2)x/(N+2). The checker takes N=128N=128, squares back the required number of times, and uses e−x=1/exe^{-x}=1/e^x for negative arguments.

  • Machin's identity π=16arctan⁡(1/5)−4arctan⁡(1/239)\pi=16\arctan(1/5)-4\arctan(1/239) reduces π\pi to two alternating rational series. In each case the next term bounds the remainder after the first 240 terms. The identity follows from the tangent addition formula and the fact that 4arctan⁡(1/5)−arctan⁡(1/239)4\arctan(1/5)-\arctan(1/239) lies in (0,π/2)(0,\pi/2) and has tangent one.

Monotonicity allows logarithms and exponentials to be evaluated at the two interval endpoints. Every series operation and every later operation uses directed integer rounding.

For root isolation, the checker encloses FF at both rational endpoints displayed above and verifies

F(545439823.214)<1500000001<F(545439823.216).F(545439823.214)<1500000001<F(545439823.216).

It also checks that this interval lies above 2π2\pi. Since F′(T)=log⁡(T/(2π))/(2π)>0F'(T)=\log(T/(2\pi))/(2\pi)>0 there, the specified root is inside it. This proves a statement about the elementary function FF only. The separate assertion F(A)=N(A)F(A)=N(A) and the zero verification remain external.

Next the checker constructs Rm(δ),T1,z,A′R_m(\delta),T_1,z,A' and every coefficient of Theorem 1. It checks 0<mδ<1−e−500<m\delta<1-e^{-50} and T1≥158.84998T_1\ge158.84998, and verifies

17exp⁡5019R<A.17\exp\sqrt{\frac{50}{19R}}<A.

Thus Y=AY=A exactly, and the second line of Ω2\Omega_2 simplifies to Rm(δ)R(A)ϕm(A)R_m(\delta)\mathcal R(A)\phi_m(A). It substitutes the full integral upper bounds for K1,K2K_1,K_2, using A′>1A'>1 and positive coefficients. No quadrature or unbounded tail truncation is used.

Finally, it encloses this explicit upper-bound expression ε^\widehat\varepsilon and checks its upper endpoint is strictly below the rational target in (1). The output's integral-bound intervals enclose the elementary upper expressions, not the exact integrals from below. Likewise, the recorded two-sided interval encloses ε^\widehat\varepsilon, while the source's ε\varepsilon is only asserted to be at most that upper expression. This distinction avoids presenting a one-sided bound as an exact evaluation.

The same checker verifies the finite endpoint inequalities used in the range calculations. Those checks concern only elementary real functions. It does not enumerate primes through 101110^{11}, verify zeta zeros, or reprove the external explicit-formula theorem.