Cell Reference To Previous Sheet?

We have a sizeable Excel workbook that contains many worksheets for various things, everything works smoothly except for one minor niggle.

I am looking for a formula that references to a cell on a previous worksheet, the worksheet could be named anything (eg A1, B, 2, 3.4, etc). Then to add 1, ideally the first worksheet inserted must equal, say, 0 BUT can reference the sheet previous as this is a constant; so something along the lines of...

Cell A1 =magic formula
Cell A2 =A1+1

This is to get a vlookup to work consistently.

OR another option is, for the worksheet to reference an already populated worksheet and read down a table by adding one to reference the cells. Eg first sheet reads ='schedule'!A13, the next sheet added would read A14 then A15 etc...

OR a worksheet (like page numbers) count into a cell onto each worksheet inserted, eg on worksheet 6 in cell A1 the number 6 would be inserted then worksheet 7 would have 7 inserted into A1 etc..