A Divisor-Sum Analogue of the Collatz Map

Let $σ$ denote the sum-of-divisors function and let $\mathcal{R}$ send an odd integer $n$ to $σ(n)$ and an even integer $n$ to $n/2$. We conjecture that every orbit of $\mathcal{R}$ reaches $1$; this implies that there is no odd $2^{k}$-perfect number for any $k \ge 1$. We prove a pointwise descent