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We investigate the integer solutions of Diophantine equations related to perfect numbers. These solutions generalize the example, found by Descartes in 1638, of an odd, ``spoof perfect factorization $3^2cdot 7^2cdot 11^2cdot 13^2cdot 22021^1$. More recently, Voight found the spoof perfect factorization $3^4cdot 7^2cdot 11^2cdot 19^2cdot(-127)^1$. No other examples appear in the literature. We compute all nontrivial, odd, primitive spoof perfect factorizations with fewer than seven bases -- there are twenty-one in total. We show that the structure of odd, spoof perfect factorizations is extremely rich, and there are multiple infinite families of them. This implies that certain approaches to the odd perfect number problem that use only the multiplicative nature of the sum-of-divisors function are unworkable. On the other hand, we prove that there are only finitely many nontrivial, odd, primitive spoof perfect factorizations with a fixed number of bases.
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Let $f(n)$ and $g(n)$ be the number of unordered and ordered factorizations of $n$ into integers larger than one. Let $F(n)$ and $G(n)$ have the additional restriction that the factors are coprime. We establish the asymptotic bounds for the sums of $F(n)^{beta}$ and $G(n)^{beta}$ up to $x$ for all real $beta$ and the asymptotic bounds for $f(n)^{beta}$ and $g(n)^{beta}$ for all negative $beta$.
We classify the dual strongly perfect lattices in dimension 16. There are four pairs of such lattices, the famous Barnes-Wall lattice $Lambda _{16}$, the extremal 5-modular lattice $N_{16}$, the odd Barnes-Wall lattice $O_{16}$ and its dual, and one pair of new lattices $Gamma _{16}$ and its dual. The latter pair belongs to a new infinite series of dual strongly perfect lattices, the sandwiched Barnes-Wall lattices, described by the authors in a previous paper. An updated table of all known strongly perfect lattices up to dimension 26 is available in the catalogue of lattices.
The concept of a covering system was first introduced by ErdH{o}s in 1950. Since their introduction, a lot of the research regarding covering systems has focused on the existence of covering systems with certain restrictions on the moduli. Arguably, the most famous open question regarding covering systems is the odd covering problem. In this paper, we explore a variation of the odd covering problem, allowing a single odd prime to appear as a modulus in the covering more than once, while all other moduli are distinct, odd, and greater than $1$. We also consider this variation while further requiring the moduli of the covering system to be square-free.
M. B. Levin used Sobol-Faure low discrepancy sequences with Pascal matrices modulo $2$ to construct, for each integer $b$, a real number $x$ such that the first $N$ terms of the sequence $(b^n x mod 1)_{ngeq 1}$ have discrepancy $O((log N)^2/N)$. This is the lowest discrepancy known for this kind of sequences. In this note we characterize Levins construction in terms of nested perfect necklaces, which are a variant of the classical de Bruijn necklaces. Moreover, we show that every real number $x$ whose base $b$ expansion is the concatenation of nested perfect necklaces of exponentially increasing order satisfies that the first $N$ terms of $(b^n x mod 1)_{ngeq 1}$ have discrepancy $O((log N)^2/N)$. For base $2$ and the order being a power of $2$, we give the exact number of nested perfect necklaces and an explicit method based on matrices to construct each of them.
Some new results concerning the equation $sigma(N)=aM, sigma(M)=bN$ are proved. As a corollary, there are only finitely many odd superperfect numbers with a fixed number of distinct prime factors.
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