Nikolaos Mavrotheris

Characteristic-Vector Congruences for Weak Primary Pseudoperfect and Giuga numbers

Let $\mu\in\{-1,1\}$, and suppose that an integer $n>1$ satisfies \[a:=\frac{\mu}{n}+\sum_{p\mid n}\frac1p\in\mathbb Z.\] Writing $r=\omega(n)$ for the number of distinct prime divisors of $n$, we associate to $(n,a,\mu)$ an integral unimodular star lattice of determinant $\mu$ a...