Per PA help:  https://revenue-pa.custhelp.com/app/answers/detail/a_id/1470/~/how-do-i-know-if-the-amount-on-my-109...

A code of 4 indicates the IRA/Pension was received due to death of the original owner.  Either select "death" or "I qualify, plan qualify" as the retirement plan distribution is not taxable on a PA income tax return.

The "A"  indicates that the distribution is eligible for the special 10 year averaging treatment on a federal return.  See https://ttlc.intuit.com/questions/4318825-ten-year-averaging-of-401k-pension-who-can-use-it   for details and eligibility.