It said that the quantity sum(1/(n log n) for n in A) is always finite when A is a primitive set. The "operation done to each element of the set" is n -> 1 / (n

It said that the quantity sum(1/(n log n) for n in A) is always finite when A is a primitive set. The "operation done to each element of the set" is n -> 1 / (n log n).