Loop over a tag by i+1

[poou]

I want to download multiple items which have different a tags. For example:
First is: [a]
Second is: [a2]
Third is: [a3] and so on…
I wondered if there is a way to increase a by one such as [a+1] for each loop.

[Plankton]

For how to increment a variable (add 1) see here:

Increase value +1 per loop

To increase loop or others variable you can use this command { "Command": "executeScript_Sandbox", "Target": "return Number (${Loop_Counter}) + 1", "Value": "Loop_Counter" },

[poou]

I have read it but I have no idea where to paste that code and how can it interact with my a or div tag.