A simple notation question: I'm familiar with the notation $a \propto b$, which means $a$ and $b$ are constant multiples of each other, but is there an analogous symbol for when $a$ and $b$ differ by a constant? For instance, when $a \propto b$, what symbol belongs between $\log a$ and $\log b$? Is there one?
EDIT: recalling Knuth's up arrow, it occurs to me that there might be similar notation for the relationship $a[n]k = b$, for any hyperoperation $[n]$ and constant $k$. Is $a \propto^{(n)} b$ accepted notation? Admittedly, it's hard to imagine this being very useful beyond $n=1,2,3$ (addition, multiplication, exponentiation).