Notation for an indecomposable module. If $V$ is a 21-dimensional indecomposable module for a group algebra $kG$ (21-dimensional when considered as a vector space over $k$), which has a single submodule of dimension 1, what is the most acceptable notation for the decomposition of $V$, as I have seen both $1\backslash 20$ and $20/1$ used (or are both equally acceptable)?

$V=1\backslash 20$? The 20/1 and 1\20 notation "for a module" looks nonsensical and bad for a few reasons, but then again math is a huge subject, so I could just be suffering from limited experience.
Is the idea of $1\backslash 20$ to say "$V$ has one submodule of codimension 20"? If so I imagine they have a better way of writing this than "module=number\number".
If $V$ had a single submodule $S$, I would talk about the quotient $V/S$, and its dimension $\dim (V/S)=20$.
