I would like to preallocate some static arrays for use with DifferentialEquations.jl. My problem uses a lot of matrices that are 3 x N, where N is not known ahead of time. I would like to use StaticArrays.jl and do something like:

```
struct Memory{N}
f::MArray{Tuple{3,N},Float64,2,3N}
g::MArray{Tuple{3,N},Float64,2,3N}
...
end
```

Unfortunately, 3N, the number of entries, does not work as N is not seen as an integer but a type. Is there a good way to do this?