First of all, pi is considered just as pi only. It is not taking the value of i from the for loop.
If you want to create, for example p39, then use something like paste0("p", i).
But it'll be a string, and you have to tell R to search for the variable with this name. For that you need get.
So, try this: print(get(paste0("p", i)))
Hope this helps.