User blog comment:Alejandro Magno/Make an extension of the notation remake 2/@comment-5029411-20141022114149/@comment-25371339-20141022180027

So a[n,,,...,,,m] = a[n,,,...,,n,,,...,,n,,,...,, ... ,,,...,,n,,,...,,n,,,...,,] with m entries.

Next step is rows of commas:

a[n,(1),m] = a[n,,,...,,,n] with m commas

a[n,,(1),m] = a[n,(1),n,(1),n,(1),...,(1),n,(1),n,(1),n] with m entries

a[n,(1),,m] = a[n,,,...,,,(1),n] with m commas

a[n,(1),(1),m] = a[n,(1),,,...,,,n] with m commas

etc.