Trouble joining a formula to be direct and indirect

I have a formula that references a cell in a different sheet called "allocation". I want to be able to copy the formula into a new workbook and have it reference the same sheet name ("allocation") in the new workbook. I'm using this formula so far:

=INDIRECT("'allocation'!A10")

This works but I also want it to change the A10 as the formula is copied down a column.
The INDIRECT formula stops that from happening. How can I combine the indirect reference to sheet name but allow a10 to change all in the same formula?

I tried this:
=INDIRECT("'allocation'!")&A10
but it doesn't combine the two like I want it to.