I have recently applied for a postdoc call with financial support from goverenment not from a mentor for a specific project. In the application from there was a table to write about number of publications. I want to know about the normal range of number of expected papers to be published? In the field of Pure Mathematics and Mathematical physics. The period of postdoc is 3 years.
Even within pure math, a "paper" is a very variable unit of work. I've got one publication which took maybe 5h of my time and was published within 5 months of me starting to work on it; and I've got one where my estimate is that I spend around 1000h over a 10 year period on it. Length-wise, I've got something with 3 pages and something with over 100.
With the disclaimer out of the way, the number that came to my mind when reading your question is approximately 5 papers. That seems to me as the ballpark for how many papers you can actively/reliablishly plan for in a 3 years period without committing to any salami slicing. But a concrete project may have different predictions going along with it.