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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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The imported dyadic theorem says that for u,v>0u,v>0 with u/vu/v irrational, every sufficiently large integer can be written as

∑r∈R⌊u2r⌋+∑s∈S⌊v2s⌋,\sum_{r\in R}\lfloor u2^r\rfloor+ \sum_{s\in S}\lfloor v2^s\rfloor,

where R,SR,S are finite subsets of the nonnegative integers. An index is used once in each ray; equal values at different indices are permitted by that theorem. Its recorded acceptance is on the dyadic claim page.

Fix m,t,L,Fm,t,L,F as in L33 and put γ=21/m\gamma=2^{1/m}. A rational mmth root of an integer is an integer, and no integer has mmth power 22 for m≥2m\ge2. Thus γ\gamma is irrational and 1<γ<21<\gamma<2.

Choose an integer j≥Lj\ge L so large that

tγn(γ−1)>1(n≥j),⌊tγj⌋>max⁡(F∪{0}).t\gamma^n(\gamma-1)>1\quad(n\ge j), \qquad \lfloor t\gamma^j\rfloor>\max(F\cup\{0\}).

These inequalities are possible because t>0t>0 and γ>1\gamma>1. The floor values with indices at least jj are positive, strictly increasing, and outside FF.

Set u=tγju=t\gamma^j and v=tγj+1v=t\gamma^{j+1}. Both are positive and u/v=γ−1u/v=\gamma^{-1} is irrational. Since γm=2\gamma^m=2,

⌊u2r⌋=⌊tγj+mr⌋,⌊v2s⌋=⌊tγj+1+ms⌋.\lfloor u2^r\rfloor=\lfloor t\gamma^{j+mr}\rfloor, \qquad \lfloor v2^s\rfloor=\lfloor t\gamma^{j+1+ms}\rfloor.

The classes j+mrj+mr and j+1+msj+1+ms are disjoint for m≥2m\ge2. Consequently each representation given by the dyadic theorem uses distinct indices of the original tail. Strict increase on that tail makes their integer values distinct as well. All those values are positive and avoid FF, which proves L33.

For Problem 354(ii), choose m=2m=2 and t=αt=\alpha. Completeness of this single ray implies completeness after adjoining the β\beta ray for every β>0\beta>0, whether or not α/β\alpha/\beta is irrational. The argument works with first index 00 or 11 and with either indexed or distinct-value sums. The threshold is allowed to depend on every fixed parameter and the finite deletion. No assertion for arbitrary γ∈(1,2)\gamma\in(1,2) follows.