n is the max number of nodes.

p is the number of address stored per entry.

d is the overhead of a level

p=1 it just stores 1 address of a node managing the block and d = 0 then for 64 address space that is 16k bytes

this a O(log(n)^2) memory per node

use the 128 bit address space of ip6  just 4 mebibytes is enough to store a 128 path for each entry that means it would only need a average branching factor of 2