I am amending my returns for 2013-2015. Where do I find the tax tables for those years when doing the form 1040X by hand? 1040x no files found

These tax tables can be found in the 1040 instructions for those years at the IRS web site.

The problem is that those same tax tables will not match your computations. I know because I just finished looking at 2016 and 2017 tax tables, which are based on ordinary income. (In my case, I had substantial capital gains). A person using those tables would pay substantially more than yours - in 2016, I would have owed 98 and 528 in 2017!