Density conjecture for sums of distinct powers

Let s1s\ge1 and let AA be a sequence of integers at least 22. For a sequence SS of positive integers, write

Σ(S)={i=1εisi: εi{0,1}, i=1εi<},\Sigma(S)=\left\{\sum_{i=1}^{\infty}\varepsilon_i s_i:\ \varepsilon_i\in\{0,1\},\ \sum_{i=1}^{\infty}\varepsilon_i<\infty\right\},

and let Pow(A;s)\operatorname{Pow}(A;s) be the sequence of powers aka^k with aAa\in A and ksk\ge s.

Density conjecture for sums of distinct powers. If every pair a1,a2Aa_1,a_2\in A satisfies gcd{a1,a2}=1\gcd\{a_1,a_2\}=1 and

aA1loga>log2,\sum_{a\in A}\frac1{\log a}>\log 2,

\nthen Σ(Pow(A;s))\Sigma(\operatorname{Pow}(A;s)) has positive lower asymptotic density.

The question follows a result constructing complete power sequences even when the reciprocal sum aA1/(a1)\sum_{a\in A}1/(a-1) is arbitrarily small. The conjectured positive-density conclusion is not established in the source.

Sources & referencesView supporting material

Primary source

Giuseppe Melfi, “On certain positive integer sequences”, arXiv:math/0404555 (2004).

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