User blog comment:Googleaarex/Aarex's Ultra Array Notation/@comment-24509095-20140411065246

Aarex:

1. Where did the d come from in Rule S2?

2. I know where to use Rule S5 but the definition seems to be incomplete.

3. Can you explain Rule S7?

4. Look at this:

$$\{3, 3[1[2]2]2\}$$

$$\{<3, 3, [1[2]2]2>\}$$

$$\{<3, 3>[1[2]2]2\}$$

$$\{<3, 3>[1[1][1[1][1[1]3[2]2][2]2][2]2]\}$$

$$\{<3, 3>[1[1][1[1][4[2]2][2]2][2]2]\}$$

What's next? No rules apply.